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Herbal Therapy in Dermatology
Monica K. Bedi, MD;
Philip D. Shenefelt, MD
Arch Dermatol. 2002;138:232-242.
ABSTRACT
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Herbal therapy is becoming increasingly popular among patients and physicians.
Many herbal preparations are marketed to the public for various ailments including
those of the skin. Herbal therapies have been used successfully in treating
dermatologic disorders for thousands of years in Europe and Asia. In Germany,
a regulatory commission oversees herbal preparations and recommended uses.
In Asia, herbal treatments that have been used for centuries are now being
studied scientifically. Currently, the United States does not regulate herbal
products, as they are considered dietary supplements. Therefore, there is
no standardization of active ingredients, purity, or concentration. There
are also no regulations governing which herbs can be marketed for various
ailments. This has made learning about and using these treatments challenging.
Information compiled in a practical fashion may enable more patients to benefit
from these treatments currently used worldwide. We reviewed the herbal medications
that show scientific evidence of clinical efficacy, as well as the more common
herbs shown to be useful in the treatment of dermatologic disorders. The safety
of each herb has been addressed to better enable the physician to know which
herbal therapies they may want to begin to use in practice. Common drug interactions
and side effects of herbal medicines that may be seen in the dermatologic
setting were also studied.
INTRODUCTION
Herbal medicine dates back thousands of years. It originated in India
and China and it is still widely used in Asia. In India, Ayurvedic medicine
dates back to 3000 BC. Ayurvedic medicine combines physiological and holistic
principles. It is based on the concept that the human body is composed of
5 energy elements that also make up the universe: earth, water, fire, air,
and space. Interaction of these elements gives rise to the 3 doshas (forces), 7 dhatus (tissues), and 3 malas (waste products). All diseases are attributed to
an imbalance between the 3 doshas. Diagnosis is made
by an elaborate system of examination of the physical findings, the pulse,
and the urine, as well as an 8-fold detailed examination to evaluate both
the physical and mental aspects of the condition. Treatment is then individually
tailored to the findings.1
Chinese medicine dates back about 4000 years and is aimed at treating
the whole person. It is based on the complementary forces yin and yang. In healthy individuals, the yin and yang are in balance, and
illness occurs when there is inequality between the forces. The Chinese evaluate
the exchange between the environment and the body, such as food, drink, and
air into the body and waste leaving the body. Special attention is placed
on the physical examination of the tongue, iris, and pulse of the individual
to determine the cause of the imbalance and then to determine the appropriate
individual treatment. Treatment is usually a mixture of herbs, massage, and
acupuncture.2
In Western medicine, herbal therapy began as folk medicine. In the United
States, it began in the colonial days, when homemade botanicals were provided
by the women in the home.3 Native American
use of botanical treatments also greatly influenced the use of herbal therapy
in the United States. In the 19th century, these traditions were expanded
and used by a group of physicians known as the Eclectics. As herbal medicine
has developed in the United States, it has also been influenced by European
and Chinese practices.4
Herbal therapy has recently become increasingly popular among patients
seeking alternative treatment options. The number of visits to alternative
medicine practitioners in the United States is growing rapidly. In 1997, the
number of visits was estimated to be 629 million, which exceeded the number
of visits to all primary care physicians.5
Approximately $27 billion was spent out of pocket for these alternative therapies
in 1997, and $3.24 billion of this was spent on herbal therapy.6
It is estimated that about 50% of the population uses some form of alternative
medicine, and many patients do not share this information with their physicians.
In a previous survey, those most likely to use unconventional treatment modalities
were nonblack, college educated, and between the ages of 25 and 49 years and
had an annual income greater than $35 000.7
Most patients seeking the alternatives do so because conventional therapy
has failed or they feel there are fewer side effects, as the products are
natural. This recent increase in alternative medicine has led to more research
and education on the subject to enable physicians to better inform and care
for their patients.
In the United States, herbal remedies are sold as dietary supplements,
and standards of potency and efficacy are not currently required. In Germany,
a regulatory authority known as Commission E has performed an extensive review
of common botanicals. The commission has evaluated the quality of evidence,
clinical efficacy, and uses of 300 herbal preparations.8-9
This evaluation has led to standardization of herbal treatments. Several herbal
therapies for dermatologic conditions have stood the test of time for their
efficacy and some show significant scientific evidence of usefulness. In this
day of advanced communication between physicians worldwide, it is important
that we share information on herbal therapy, effects, and interactions, so
that we may offer alternatives to our patients.
ACNE
Tannins
Tannins have been used topically to treat acne because of their natural
astringent properties. Witch hazel (Hamamelis virginiana) bark extract is commonly used by making a decoction from 5 to 10
g of herb in 1 cup (0.24 L) of water. Witch hazel is considered very safe
to use topically.10 Other similar astringents
can be made from white oak tree or the English walnut tree. These preparations
should be strained before use and can be used 2 or 3 times per day. Commercially
available preparations are not recommended, as the tannins are lost in the
distillation process.11
Fruit Acids
Fruit acids, such as citric, gluconic, gluconolactone, glycolic, malic,
and tartaric acids, have been used topically and have shown promise in treating
acne because of their exfoliative properties. In one study, gluconolactone
was as effective in clearing inflamed and noninflamed acne lesions as 5% benzoyl
peroxide and more effective than placebo.12
Irritation is the main adverse effect, especially in higher concentrations.
Tea Tree Oil
Tea tree oil may also play a role in topical acne treatment. It is an
essential oil extracted from the leaves of Melaleuca alternifolia, a small tree indigenous to Australia. It contains approximately 100
compounds, mainly plant terpenes and their corresponding alcohols.13 In 1990, a study of 124 patients compared 5% tea
tree oil in a water-based gel with 5% benzoyl peroxide. Although the tea tree
oil did not work as quickly as benzoyl peroxide, it did show statistical improvement
in the number of acne lesions at the end of 3 months. Also, there was a significantly
lower incidence of adverse effects such as dryness, irritation, itching, and
burning with the tea tree oil (44%) than with benzoyl peroxide (79%).10(p629) There are occasional reports of allergic contact
dermatitis and of poisoning if taken internally.14-18
However, the degradation products of monoterpenes in the tea tree oil actually
appear to be the sensitizing agents.19 Therefore,
topical treatment is considered very safe.
Vitex
Vitex (Vitex agnus-castus) taken orally has
been shown to be effective in treating premenstrual acne. The whole-fruit
extract is thought to act on follicle-stimulating hormone and luteinizing
hormone levels in the pituitary to increase progesterone levels and reduce
estrogen levels. The German Commission E monographs recommend 40 mg/d. The
main adverse effects reported are gastrointestinal tract upset and rash. It
should not be taken by pregnant or nursing women.20(p176)
The German Commission E has also approved topical bittersweet nightshade (Solanum dulcamara) and orally administered brewer's yeast
(Saccharomyces cerevisiae) for the treatment of acne
because of their antimicrobial effects.20(p88,118)
In China, topical duckweed (Lemma minor) is used
to treat acne.20(p258)
WOUNDS AND BURNS
Aloe Vera
Aloe vera leaves produce 2 substances, a gel and a juice or latex. The
gel is obtained from the inner part of the leaf and has been used topically
for centuries for the treatment of wounds and burns. The juice or latex refers
to a bitter yellow fluid extracted from the specialized areas of the inner
leaf skin and is generally sold as a powder that has very potent laxative
effects.10(p31)
Several case reports and animal studies have demonstrated that aloe
vera reduces burning, itching, and scarring associated with radiation dermatitis.21 It has also been shown to accelerate healing of chronic
leg ulcers, surgically induced wounds, and frostbite. The mechanism of action
has been studied by in vivo animal studies. Aloe vera decreases thromboxane
A2, thromboxane B2, and prostaglandin 2 , which
cause vasoconstriction and platelet aggregation. This is thought to increase
dermal perfusion, reducing the risk of tissue loss from ischemia.21 In vitro studies have shown a carboxypeptidase that
inactivates bradykinin (potent pain-inducing agent at sites of acute inflammation),
thereby possibly decreasing pain at the treatment site.22
Salicylic acid has been shown to be present in aloe vera; it acts as an analgesic
and anti-inflammatory by inhibiting prostaglandin production.23
Magnesium lactate is also present in aloe vera. It is thought to act as an
antipruritic by inhibiting histidine decarboxylase, which controls the conversion
of histidine to histamine in mast cells.21
Relief of inflammation is also thought to be due to the immunomodulatory properties
of the gel polysaccharides, especially the acetylated mannans.24
Aloe vera has also shown bactericidal and antifungal activity in vitro. The
main adverse effect of topical aloe vera gel is allergic contact dermatitis.
There have also been reports of delayed healing after laparotomy or cesarean
section. Taken orally, aloe vera is considered very safe when used properly.25(p7)
Honey
Honey has been used topically for centuries to accelerate wound healing.
It has been reported to be helpful in treating burns, decubitus ulcers, and
infected wounds.26 In vitro it has been shown
to have antibacterial and antifungal activity to organisms commonly infecting
surgical wounds.27 In 1998, a small study was
performed of 9 infants with large, open, culture-positive postoperative wound
infections in which standard treatment (>14 days of appropriate intravenous
antibiotics and cleansing with chlorhexidine) failed. These wounds were then
treated with 5 to 10 mL of fresh unprocessed honey twice a day. By day 5,
there was marked clinical improvement, and by day 21, the wounds were all
closed, clean, and sterile.28 In another randomized
controlled trial, honey-impregnated gauze was compared with a polyurethane
film (OpSite; Smith & Nephew, North Humberside, England) for partial-thickness
burns. The honey-treated wounds healed statistically earlier (mean, 10.8 days
vs 15.3 days) and with equal complications such as infection, overgranulation,
and contracture compared with the polyurethane film–treated wounds.29 The wound-healing properties of honey are thought
to result from the debriding properties of the enzyme catalase, absorption
of edema because of honey's hygroscopic properties, its ability to promote
granulation and reepithelialization from the wound edges, and its antimicrobial
properties.30 Although there have been reports
of contact dermatitis to honey, there have been no reports of significant
adverse effects.30
Marigold
Calendula officionalis, more commonly known
as marigold, has been used topically since ancient times and is currently
approved by the German commission as an antiseptic and to heal wounds.9(p119) Contemporary herbalists continue to recommend
a topical preparation for the treatment of wounds, ulcers, burns, boils, rashes,
chapped hands, herpes zoster, and varicose veins. Gargles are also popular
for mouth and throat inflammation.10(p129)
It is widely accepted as a topical treatment for diaper dermatitis or other
mild skin inflammation.31 This is treated with
an application several times a day of an ointment or cream made by mixing
2 to 5 g of the flower heads with 100 g of ointment. A gargle or lotion can
also be used, which is made by mixing 1 to 2 tsp (5-10 mL) of tincture with
0.25 to 0.5 L of water.10(p130) The main adverse
effect is allergic contact dermatitis. No serious adverse effects have been
reported, and it is considered safe to use both topically and orally.25(p22)
The anti-inflammatory effects of marigold are thought to be due to the
triterpenoids. In animal studies Calendula appears
to stimulate granulation and increase glycoproteins and collagen at wound
sites.31 It also shows in vitro antimicrobial
and immune-modulating properties.10(p130)
Tannins
There are also many herbs containing tannins that act as astringents,
thereby helping to dry oozing and bleeding wounds. Some of the more commonly
reported tannin-containing herbs that may be helpful for the topical treatment
of wounds include English walnut leaf, goldenrod, Labrador tea, lavender,
mullein, oak bark, rhatany, Chinese rhubarb, St John's wort, and yellow dock.10(p709)
HERPES SIMPLEX
Balm
Balm (Melissa officinalis) is a lemon-scented
member of the mint family. The leaves can be steam distilled to produce an
essential oil. Topical uses include treating herpes simplex and minor wounds.
In a randomized double-blind trial of 116 patients with herpes lesions, 96%
had complete clearing of lesions at day 8 after using 1% balm extract cream
5 times a day.32 In another trial, balm extract
was placed on lesions within 72 hours of onset of symptoms. The size of the
lesions and healing time were statistically better in the group treated with
balm.31 A tannin and polyphenols appear to
be responsible for its antiviral effect.10(p58)
Balm appears very safe to use both topically and orally.10(p58),25(p75) Other herbal preparations have also shown test
tube activity against herpes simplex, but clinical studies have not yet been
performed. These include Echinacea, sweet marjoram,
peppermint, and propolis.10(p702)
Licorice and Hibiscus
Herpes zoster and postherpetic neuralgia have been treated with a topical
licorice (Glycyrrhiza glabra, Glycyrrhiza uralensis) gel preparation.33(p155-156)
Glycyrrhizen, one of the active components of licorice, has been shown to
inhibit replication of varicella zoster.34
However, there have been no clinical studies to support this. Topical use
appears very safe, but care should be used when it is taken orally.25(p58) In China, herpes zoster is commonly treated
topically with hibiscus (Hibiscus sabdariffa).20(p394) This has been shown to be very safe topically
and orally.25(p61)
BACTERIAL AND FUNGAL INFECTIONS
Tea Tree Oil
Tea tree oil (see the "Acne" section for a description) has been widely
used topically for the treatment of bacterial and fungal infections. Tea tree
oil has shown in vitro activity against a wide variety of microorganisms,
including Propionibacterium acnes, Staphylococcus aureus, Escherichia coli, Candida albicans, Trichophyton mentagrophytes, and Trichophyton rubrum.35-36
In a randomized double-blind trial of 104 patients, 10% tea tree oil cream
was compared with 1% tolnaftate cream and placebo cream. Symptomatic relief
was comparable in the tea tree oil and the tolnaftate groups; however, there
was significantly greater mycologic cure in the tolnaftate group (85%) than
the tea tree oil group (30%). Cure rates between the tea tree oil and placebo
groups were not statistically different.37
Another randomized double-blind study of 117 patients compared a solution
of 100% tea tree oil with 1% clotrimazole solution in the treatment of onychomycosis.
After 6 months of treatment, the 2 groups showed comparable results on the
basis of mycologic cure (11% for clotrimazole and 18% for tea tree oil) and
clinical assessment and subjective rating of appearance and symptoms (61%
for clotrimazole and 60% for tea tree oil).38
Therefore, tea tree oil may have a role in at least symptomatic treatment
of tinea pedis and onychomycosis and other superficial wounds. However, it
should not be used for burns because of its cytolytic effect on epithelial
cells and fibroblasts.39
Garlic
Garlic (Allium sativum) contains ajoene, which
has been shown to have antifungal activity. In a study of 34 patients treated
with 0.4% ajoene cream topically once a day for tinea pedis, 79% noted clearing
within 7 days and the remainder had clearing within 14 days. At a 3-month
follow-up, all participants remained free of fungus.40
There are reports of contact dermatitis with frequent topical exposure.20(p328) Oral administration should be avoided while
breastfeeding.25(p6) There are also reports
of prolonged bleeding when garlic is taken orally.20(p328)
SCABIES
Certain other common dermatologic infections have been treated for centuries
with herbal preparations. Anise (Pimpinella anisum)
seeds are a source of an essential oil that has displayed antibacterial and
insecticidal activity in vitro and has been used topically to treat scabies
and head lice. It should not be used in pregnancy.25(p86)
Neem (Azadirachta indica) is indigenous to India,
and every part of the plant has been used medicinally. In a report of more
than 800 villagers in India, a paste of neem and turmeric applied topically
appeared to treat chronic ulcers and scabies.10(p452)
It appears safe in adults, but it can be poisonous to children.10(p453)
Numerous other herbs have been used for centuries in India and China to treat
scabies.20
CONDYLOMA AND VERRUCA VULGARIS
There are also herbal preparations for the topical treatment of condyloma
and verruca vulgaris. Podophyllin, used to treat condyloma acuminata, comes
from the root of the American mayapple (Podophyllum peltatum).20(p510) It should not be used during
pregnancy.25(p89) The German commission has
approved bittersweet nightshade (S dulcamara) and
oat straw (Avena sativa) for the treatment of common
warts.20(p88,552) Calotropis (Calotropis procera) is used in India and greater celandine (Chelidonium majus) is used in China for the treatment of warts.20(p142,170) Bittersweet nightshade and celandine should
also be avoided in pregnancy and while breastfeeding.20(p88,170)
DERMATITIS AND PSORIASIS
Chinese Herbal Medicine
Traditional Chinese herbal medicine (CHM) for the treatment of atopic
dermatitis and psoriasis has recently received much attention. In traditional
Chinese medicine, the body is treated as a whole and the aim of therapy is
to restore harmony to the functions of the body.41
This requires a mixture of various herbs individually formulated for the patient,42 making randomized controlled trials difficult to
undertake. Recently, 2 randomized placebo-controlled crossover trials were
performed in England to study the effects of orally administered CHM in the
treatment of atopic dermatitis in which traditional Western therapy had failed.42-44 The investigators
were aided by a Chinese physician who was able to create a standardized mixture
of 10 herbs useful in treating atopic dermatitis characterized by erythema,
lichenification, and plaques of dermatitis in the absence of active exudation
or clinical infection. The 10 herbs used were Potentilla
chinensis, Tribulus terrestris, Rehmannia glutinosa, Lophatherum gracile, Clematis armandii, Ledebouriella saseloides, Dictamnus dasycarpus, Paeonia lactiflora, Schizonepeta tenuifolia,
and G glabra.43 These
herbs were placed in sachets and boiled to make a decoction that was orally
administered daily as a tea. The placebo arm consisted of a decoction made
from several herbs with similar smells and tastes that have no known efficacy
in the treatment of atopic dermatitis. The first study focused on 37 children
and showed a median decrease in erythema score of 51.0% in the treatment group
compared with only a 6.1% improvement in the placebo group. The percentage
surface involvement also decreased by 63.1% and 6.2% for the treatment and
placebo groups, respectively. In this initial study, no serious adverse effects
were found. These 37 children were offered continued treatment with the CHM
and then followed up for 1 year.45 Eighteen
children completed the year of treatment and showed 90% reduction in eczema
activity scores. The children who withdrew from the study did so because of
lack of further response to treatment, unpalatability of the tea, or difficulty
in preparation of the treatment. By the end of 1 year, 7 patients were able
to discontinue therapy without relapse. Asymptomatic elevation of aspartate
aminotransferase level was noted in 2 patients, which returned to normal with
discontinuing treatment. No other serious sequelae were observed. In the other
study, the design was similar; however, the investigators studied 31 adult
patients with atopic dermatitis.42 Again, the
decrease in erythema and surface damage was statistically superior in the
treatment group compared with the placebo group. There was also subjective
improvement in itching and sleep. These patients were also followed up for
a year, with continued improvement and no serious adverse effects, whereas
the patients who discontinued treatment noted a decline in their condition.45 Although the sample sizes were limited during the
course of the study, initial results were promising for patients in whom standard
therapy failed. The main limitation appeared to be the taste and the preparation
of the decoction. It should be emphasized, however, that, although no serious
adverse effects were noted in this study, careful monitoring of complete blood
cell count and liver function is recommended, as reports of liver failure
and even death have been reported when baseline laboratory values were not
followed up.46-48
It is known that specific herbs used in these studies have anti-inflammatory,
antibacterial, antifungal, antihistaminic, immunosuppressant, and corticosteroidlike
effects. A few ingredients also are smooth muscle relaxants and inhibit platelet
activating factor. Several studies have tried to elucidate the mechanism of
action of this group of 10 herbs (Zemophyte; Phytotech Limited, Godmanchester,
England) in treating atopic dermatitis. It is known that patients with atopic
dermatitis have elevated levels of the low-affinity IgE receptor CD23 expressed
on circulating monocytes. In studies of interleukin (IL) 4–induced CD23
expression on monocytes, there appeared to be a reduction of the CD23 expression
when the cells were exposed to the aqueous herb extracts.2, 49
Another study examined immunologic markers for T cells, macrophages, Langerhans
cells, and low-affinity and high-affinity IgE receptors in biopsy specimens
of lesional skin treated with Zemophyte compared with biopsy specimens of
nonlesional skin.50 The investigators found
clinical improvement similar to that seen in the studies described above and
also found that the improvement was associated with statistically significant
reduction in CD23 antigen–presenting cells.
In a survey of patients with psoriasis at a large university dermatology
practice, 51% of patients used 1 or more alternative therapeutic modalities.51 This is compatible with previous Norwegian surveys
of patients with psoriasis.52 Herbal therapy
is one of the most frequently chosen alternative therapies. Psoriasis has
been treated for centuries with herbal preparations, both topical and oral.
There are many herbal preparations composed of furocoumarins, which act as
psoralens when combined with UV-A. One common CHM, known as Radix Angelicae dahuricae, contains the furocoumarins imperatorin, isoimpertorin,
and alloimperatorin. In a study involving 300 patients with psoriasis, this
CHM, taken orally, was combined with UV-A therapy and compared with standard
treatment of psoralen–UV-A with methoxsalen. The efficacy of the 2 treatments
was equivalent; however, there were fewer adverse effects such as nausea and
dizziness in the group treated with the CHM and UV-A.46
There are also topical preparations made from herbs that have shown systemic
efficacy against psoriasis, but are too toxic when given systemically.53 One example is the topical CHM composed of the plant Camptotheca acuminata decne. An open trial including 92
patients with psoriasis found that this CHM was statistically more effective
than 1% hydrocortisone. However, allergic contact dermatitis was seen in 9%
to 15% of the patients in the CHM group. Several other studies have compared
various Chinese herbal preparations with ethyliminum, which is a popular "Western
remedy" in China, although it is no longer used as standard therapy for psoriasis
in Western medicine. Therefore, although results were promising, there is
no applicability, since ethyliminum is no longer used or comparable with other
current therapy. More double-blind placebo-controlled trials are needed to
compare these herbal preparations with current standard Western treatment.
However, this is difficult, because the mixture of herbs prescribed varies
individually depending on the subtype of psoriasis ("blood-heat" type, "blood
deficiency dryness" type, and "blood stasis" type), which is determined in
traditional Chinese medicine by many findings, including the lesions of psoriasis,
the pulse, and the condition of the tongue.46
Aloe Vera
As previously described, aloe vera has been used for centuries for wound
healing and has recently been shown to be a potential treatment for psoriasis.
In a double-blind placebo-controlled study, 60 patients with slight to moderate
plaque psoriasis were treated topically with either 0.5% hydrophilic aloe
cream or placebo. The aloe-treated group showed statistically significant
improvement (83.3%) compared with placebo (6.6%). There were no adverse effects
in the treatment group.54
Capsaicin
The main ingredient in cayenne pepper, Capiscum frutescens or capsaicin, has also been studied for the treatment of psoriasis.
Two trials have shown that 0.025% cream used topically is effective in treating
psoriasis. The first study showed significant decrease in scaling and erythema
during a 6-week period in 44 patients with moderate and severe psoriasis.55 The second was a double-blind study of 197 patients
with psoriasis treated with the cream 4 times daily for 6 weeks. It showed
a significant decrease in scaling, thickness, erythema, and pruritus.56 The main adverse effect reported was a short-lived
burning sensation at the application site. Capsaicin is contraindicated on
injured skin or near the eyes, and Commission E suggests it not be used for
more than 2 consecutive days, with a 14-day lapse between applications.25(p23)
OTHER HERBS FOR TOPICAL USE
In Europe, especially Germany, there is much attention to the use of
topical herbal preparations as corticosteroid-sparing agents for the treatment
of skin inflammation, including dermatitis and psoriasis. Several herbs are
currently approved by Commission E for topical treatment of skin inflammation.
These include the following botanicals: Arnica (Arnica montana), German chamomile (Matricaria recutita),
bittersweet nightshade (S dulcamara), and brewer's
yeast (S cerevisia) are thought to have anti-inflammatory
and antibacterial effects. Heartseases (Viola tricolor),
English plantain (Plantago lanceolata), fenugreek
(Trigonella foenum-gaecum), and flax (Linum usitatissimum) contain mucilages, which act as emollients and
soothe. Agrimony (Agrimonia eupatoria), jambolan
bark (Syzygium cumini), oak (Quercus
rubar), walnut (Juglans regia), and St John's
wort (Hypericum montana) contain tannins and act
as astringents. Oat straw (A sativa) is also approved
for its soothing and antipuritic qualities.8-10,20
Arnica
Arnica comes from the dried flowers of A montana
or other arnica species. Although oral administration can cause severe health
hazards in even small amounts, the external preparations appear to be very
safe and effective. Arnica has been used for centuries as an anti-inflammatory
aid to rub into sore muscles and joints, bruises, insect bites, boils, inflamed
gums, acne eruptions, and hemorrhoids. It is also an ingredient found in many
seborrheic dermatitis and psoriasis preparations. When used as a compress,
1 tbsp (15 mL) of tincture is mixed with 0.5 L of water; if used as an infusion,
2 g of dried arnica is mixed with 100 mL of water. The cream or ointment preparations
should contain a maximum of 15% arnica oil or 20% to 25% tincture.9(p85),10(p45)
It has been known since the 1980s that the active ingredients of arnica
are the sesquiterpene lactones such as helanalin, 11,13-dihydrohelenalin,
chamissonolid, and their ester derivatives. It appears that these components
act to reduce inflammation by inhibiting the transcription factor nuclear
factor– B. Nuclear factor–B controls the transcription
of many genes, including cytokines such as IL-1, IL-2, IL-6, IL-8, and tumor
necrosis factor , as well as adhesion molecules intercellular adhesion
molecule 1, vascular cellular adhesion molecule 1, and endothelial leukocyte
adhesion molecule 1. It also inhibits many genes responsible for antigen presentation
and for cyclo-oxygenase II.57
Although most individuals tolerate the external preparations well, there
have been many reports of contact dermatitis. There are also several reports
of irritation when arnica is used at stronger concentrations or for longer
periods than are recommended. It is not recommended to use it on open wounds
or broken skin.25(p14) Also, it is important
to buy arnica from a reputable source, as it is a protected species in some
countries and other plants have been surreptitiously used.
German Chamomile
German chamomile (M recutita), a member of
the daisy family, has been used for centuries, internally and externally,
for almost all ailments, most notably gastrointestinal tract symptoms, oral
or skin inflammation, and dermatitis. A tea is made by using 2 to 3 tsp (10-15
mL) of dried flowers per cup of water and is taken internally or used as a
compress. Other topical preparations with cream or ointment bases have also
been used and studied in Germany.9(p324) Studies
have shown that topical chamomile is comparable with 0.25% hydrocortisone
and showed improvement in a sodium lauryl sulfate–induced contact dermatitis.31 One small double-blind trial found that chamomile
significantly decreased the surface area of wounds, and, in animal studies,
healing time was reduced with chamomile. It has also shown in vitro antimicrobial
activities.10(p157) The main adverse effect
reported is allergic contact dermatitis, and it is considered safe to use
topically and orally.25(p74)
The anti-inflammatory, wound-healing, and antimicrobial effects of German
chamomile are attributed to a blue essential oil that contains sesquiterpene
alcohol, -bisabolol, chamazulene, and flavinoids. These components
have shown anti-inflammatory and antispasmodic properties in animal studies.
This is partially attributed to the inhibition of cyclo-oxygenase and lipoxygenase
in vitro. The flavinoids also act by inhibiting histamine release from antigen-stimulated
human basophilic polymorphonuclear leukocytes.31
Bisabolol has also been shown to promote granulation tissue in wound healing.10(p157)
Mucilage-Containing Herbs
Several herbs contain a substance called mucilage, which is useful topically to soothe and act as an emollient on skin.
Mucilage quickly swells into a gooey mass when it comes in contact with water,
thereby aiding in dry or mildly inflamed skin. The material will also dry
and can be used as an herbal bandage for minor wounds. The herbs most notable
for their mucilage content are flax, fenugreek, English plantain, heartseases,
marshmallow, mullein, and slippery elm.10, 20
Oats
Oats have been used topically for several hundred years for their soothing
and antipruritic properties when placed in baths, and they are approved for
this use by the German commission.99(p97),20(p552) Colloidal oatmeal turns to a gooey mass when
mixed with liquid, thereby coating the skin and sealing in moisture. This
soothing and moisturizing property is attributed to the gluten content in
the plant. This can be useful in atopic dermatitis as well as idiopathic pruritus
of the elderly.
Tannins
As previously mentioned, several herbs contain tannins, which act as
astringents. Tannins used topically are thought to be beneficial in treating
dermatitis by coagulating surface proteins of cells, thereby reducing permeability
and secretion. The precipitated proteins also form a protective layer on the
skin.31 They may also have antimicrobial properties.
Several herbs are known to contain tannins. Some of the more commonly used
agents for the treatment of dermatitis include witch hazel, oak bark, English
walnut leaf, agrimony, jambolan bark, Labrador tea, goldenrod, lady's mantle,
lavender, mullein, rhatany, Chinese rhubarb, yellow dock, and St John's wort.
Although there is limited research on the use of these agents, one study showed
that a witch hazel extract in a phosphatidyl choline base was less effective
in reducing erythema from UV radiation and cellophane tape stripping in 24
healthy patients than 1% hydrocortisone.58
In another clinical trial, one group with atopic dermatitis (n = 36) and another
group with contact dermatitis (n = 80) compared witch hazel extract with control.
In the atopic group, the witch hazel was slightly superior in reducing inflammation
and itching. There are also anecdotal reports of witch hazel's usefulness
in treating atopic dermatitis.31
Pansy Flower
Pansy flower infusion is recommended by German health authorities for
the topical treatment of seborrheic dermatitis, especially in infants. The
infusion is made by mixing 1 to 2 tsp of flowers per cup of water and is used
as a wet dressing. Salicylic acid in concentrations of about 0.3% appears
to be the active ingredient. It also contains saponins and mucilage, which
have softening and soothing action. No adverse effects have been reported
with its topical use.10(p480)
Jewelweed
Jewelweed (Impatiens biflora) is reputed to
be useful in topically treating poison ivy contact dermatitis. However, research
results are conflicting. In a 1958 study, treatment with jewelweed was comparable
with standard treatment for poison ivy contact dermatitis; in 108 of 115 patients,
symptoms cleared within 2 to 3 days.59 However,
in a 1980 study, not only did jewelweed extract fail to reduce symptoms of
poison ivy dermatitis, but symptoms became worse, and in a recent study there
was no prophylactic effect of jewelweed in poison ivy dermatitis.60-61 Jewelweed has been mentioned to be
most helpful if applied to the area the poison ivy touched as soon after contact
as possible; however, this was not addressed in the studies. There have been
no reports of topical jewelweed causing adverse effects.10(p365)
CHRONIC VENOUS INSUFFICIENCY
Chronic venous insufficiency (CVI) is a common condition affecting at
least 10% to 15% of men and 20% to 25% of women.62
It is a source of great cost and morbidity. Compliance with current treatments
such as compression stockings is poor, which has led to the search for alternative
therapies.
Horse Chestnut
Horse chestnut seed extract (HCSE) is one of the most studied herbal
alternatives. Horse chestnut (Aesculus hippocastanum)
contains the plant compounds known as terpenes, and
the active component appears to be aescin.10(p343)
The mechanism of action appears to be related to inhibiting leukocyte activation,
an important physiological component of CVI. It is also thought to prevent
vascular leakage by inhibiting elastase and hyaluronase, which are involved
in proteoglycan degradation at the capillary endothelium.63
There have been many double-blind randomized trials of oral HCSE for patients
with CVI. It has been shown that HCSE decreases lower-leg volume as well as
calf and ankle circumference. There were also decreased symptoms such as fatigue,
tenderness, and pruritus. Another study showed relative equality of using
HCSE compared with grade II compression stockings for treatment of CVI.64 Most of these studies achieved statistically significant
results for treatment of CVI with doses of HCSE containing 100 to 150 mg of
aescin per day, most commonly taken as 50 mg twice a day. Adverse effects
reported were minimal and included gastrointestinal tract symptoms, dizziness,
headache, and pruritus. The rates of reported adverse effects were from 0.9%
to 3.0% and in several studies were not statistically different from rates
of adverse effects with placebo. Although there are no long-term studies of
oral HCSE in treating CVI and its sequelae, these results seem promising and
offer patients a safe alternative to compression stockings. In Europe, HCSE
has also been used in the form of a topical gel, lotion, or ointment to reduce
inflammation and discomfort associated with varicose veins, phlebitis, and
hemorrhoids.10(p344)
The seeds of the horse chestnut tree are poisonous and must be specially
prepared by a reputable manufacturer, such as those seeds currently on the
American market, to remove all toxins. Once the toxins have been removed,
it is considered relatively safe taken orally. There has been one case report
of drug-induced lupus attributed to Venocuran (Knoll AG, Ludwigshafen, Germany),
a drug for venous insufficiency containing HCSE.10(p344-345)
There have been reports of contact dermatitis when used topically.9(p269)
Grapeseed
In France there is also research on the use of herbs in CVI. Several
double-blind trials have studied the effects of grapeseed extract on CVI.
Grapeseed extract contains oligomeric proanthocyanidins, which are bioflavinoids
shown to be beneficial in strengthening capillaries. The dosage in the studies
varied from 50 mg orally once a day to 100 mg 3 times per day. No serious
adverse effects have been reported.20(p363-364)
Ginkgo
Ginkgo (Ginkgo biloba) has been used orally
in China for centuries and more recently in Europe and the United States for
numerous conditions, including heart disease, asthma, vertigo, tinnitus, impotence,
cerebral and vascular insufficiency, peripheral vascular disorders, dementia,
and other conditions. Much research indicates that ginkgo promotes vasodilation,
thereby improving many of the conditions above. Most of this research on ginkgo
relates to cerebral insufficiency and claudication, suggesting that it may
be more useful for these vascular disorders than for CVI.10(p293),65 Care should be used when ginkgo is taken orally,
as there have been reports of subarachnoid and intracerebral hemorrhage, as
well as increased bleeding time.20(p344)
Witch Hazel
Witch hazel (H virginiana) contains considerable
amounts of tannin, making it a useful astringent. It has been used topically
to soothe inflammation of the skin and mucous membranes in such disorders
as varicose veins and hemorrhoids. Animal research suggests that the witch
hazel extract has local styptic and vasoconstrictive effects. The alcohol
fluid extract has also been shown to cause venous constriction in rabbits;
thus, it is often used orally for CVI in Europe. Although it appears safe
when taken orally, efficacy of such treatment has not been well studied in
humans.8(pp670-672), 2525(p59)
Butcher's Broom and Sweet Clover
In addition to horse chestnut, the German commission has approved orally
administered butcher's broom (Ruscus acuteatus) and
sweet clover (Melilotus officinalisis) for relief
of symptoms associated with venous insufficiency such as pain, heaviness,
pruritus, and swelling. In animal studies, butcher's broom has been shown
to increase venous tone and also has diuretic properties. Sweet clover has
been shown to increase venous reflux.20(p132)
However, reflux is probably a misnomer, as the term
is generally used to describe a backward flow, and in the case of venous return
it would indicate undesired pooling. A better description of the effect of
sweet clover would be to say that it increases venous return. Both butcher's
broom and sweet clover appear to be safe when used as recommended.20(p132), 25(p100)
ALOPECIA
Essential Oils
Few randomized trials have studied herbal remedies for alopecia. Recently,
a randomized controlled double-blind study of 86 patients with alopecia areata
was performed.66 A mixture of essential oils
including thyme, rosemary, lavender, and cedarwood in carrier oils; grapeseed;
and jojoba (a liquid wax) was massaged into the scalp daily. The control group
massaged only the carrier oils into the scalp. Success was evaluated on the
basis of sequential photographs, by both a 6-point scale and a computerized
analysis of areas of alopecia. Overall, the treatment group had statistically
significant improvement over the control group (44% vs 15%). This improvement
compares with the success of standard treatment practices used conventionally.
There were no adverse effects.
Chinese Herbal Medicine
Another study evaluated the topical use of a Chinese herbal formula,
Dabao (Engelbert & Vialle, Venlo, the Netherlands), for the treatment
of androgenic alopecia.67 In this study, 396
patients participated in the double-blind placebo trial, which lasted 6 months.
The components of Dabao include 50% ethanol, 42% water, and 8% Chinese herbal
extracts, including saffron flowers, mulberry leaves, stemona root, fruits
of the pepper plant, sesame leaves, the skin of the Szechuan pepper fruit,
ginger root, Chinese angelica root, bark of the pseudolarix, and fruit of
the hawthorn. The components of the placebo included 50% ethanol, 48% water,
and 2% odor and coloring agents consisting of cherry laurel water, cinnamon
water, licorice syrup, sugar syrup, and a solution of burned sugar. In both
groups there was an increase in nonvellus hairs. Although the Dabao group
was statistically superior to the placebo group in number of nonvellus hairs,
the cosmetic improvement in both groups was minimal. Therefore, although there
were no reported adverse effects, improvement is unlikely.
SKIN CANCER
Tea
There has been much research on the use of teas in the prevention and
treatment of skin cancer. Tea is manufactured from the leaf and bud of Camellia sinensis. The majority of tea consumed worldwide
is in the form of black tea. However, in Asia, green tea is most commonly
consumed, and oolong tea is popular in China. Teas contain polyphenolic compounds,
which have antioxidant properties. The oxidative states of these compounds
vary between the different tea formulations. Green tea is produced from the
fresh leaves, and preparation is aimed at avoiding oxidation and polymerization
of the polyphenols. Production of black tea involves a controlled fermentation
process. Green tea has been shown in several mouse models to have anti-inflammatory
and antitumorigenic properties. This is thought to be due to the polyphenolic
constituent (-)-epigallocatechin-3-gallate. Numerous studies of green
tea and skin cancer were recently reviewed.68
It was found that topical application or oral consumption of green tea protects
against inflammation, chemical carcinogenesis, and photocarcinogenesis. Green
tea has been shown to block many mediators in the inflammatory process important
in the early steps of skin tumor promotion. It also appears that there is
inhibition of biochemical markers of chemical carcinogenesis, inhibition of
UV-induced oxidative stress, and prevention of UV-induced immunosuppression.68 There is also evidence that green tea protects against
psoralen–UV-A–induced photochemical damage to the skin.69 Therefore, many cosmetics and skin care products
recently have been supplemented with green tea. However, more research in
humans is needed to understand the true benefits.
There is also evidence that black tea may play a role in the prevention
of skin tumors. It appears that the theaflavins are the active components
in chemoprevention.70 Several studies have
provided evidence that topical application of constituents in black tea can
decrease UV-B–induced erythema, inhibit tumor initiation, and act as
an antitumor promoter.71-72 Oral
administration of black tea also appears to inhibit tumor proliferation and
promotes tumor apoptosis in nonmalignant and malignant skin tumors.73 A recent survey of older patients compared tea consumption
and history of squamous cell carcinoma. There was a lower risk of squamous
cell carcinoma in patients who consumed hot black tea than in nonconsumers.74 Studies comparing the effectiveness of black and
green teas in protecting against UV-induced skin tumors are conflicting as
to which is more beneficial.75-78
However, it does appear that caffeinated teas are more protective than decaffeinated
teas and that caffeine alone has some inhibitory effects on UV-B–induced
carcinogenesis.76-78
Rosemary
There are also a few reports of other herbs playing a role in the prevention
of skin tumors in mice. Rosemary (Rosmarinus officinalis) extract has been reputed to have antioxidant activity. Recently,
a methanol extract of the leaves was evaluated for its effects on skin tumors
in mice. It was found that topically applied rosemary inhibited induction
and promotion of skin tumors in mice treated with known chemical carcinogens.
Although the exact mechanism of action is still under study, it appears that
several components of the extract are important in this process. This finding
suggests that it was not the antioxidant properties alone that were beneficial
in the prevention of skin tumors.79 Rosemary
should not be used in pregnancy.25(p99)
Propolis
Propolis is a resinous material produced by honeybees from the buds
and bark of certain plants and trees. It has been used for centuries for antimicrobial,
anti-inflammatory, analgesic, and antitumor effects. These properties are
thought to be due to the flavinoid and related phenolic acids that are components
of propolis. Recently, a tumoricidal component, clerodane diterpenoid, was
isolated. This compound was studied for its topical effects on skin tumorigenesis
in mice. Clerodane diterpenoid appeared to reduce the incidence of chemically
induced dysplastic papillomas by inhibiting the synthesis of DNA in a de novo
pathway and by suppressing the growth of tumors by decreasing DNA synthesis
in a salvage pathway.80
Red Ginseng
Red ginseng is a classic traditional Chinese medicine thought to enhance
immune function of the body. In a recent study, red ginseng extracts used
topically appeared to inhibit chemically induced skin tumors in mice. This
is thought to be due to immune-modulating properties of the red ginseng.81
Silymarin
Silymarin is a flavinoid isolated from milk thistle (Silybum marianum) and is approved by the German commission for liver
disease because of its antioxidant properties. Recently, a study was performed
to assess whether this antioxidative effect would protect against tumor promotion.
Topically applied silymarin appeared to possess high protective effects against
chemically induced skin tumor promotion in mice. This may involve inhibition
of promoter-induced edema, hyperplasia, and proliferation as well as the oxidant
state.82 These results are promising, yet more
research involving human models is needed. Silymarin appears to be safe to
use topically and orally when used appropriately.25(p107)
ADVERSE EFFECTS OF HERBAL THERAPY
Many patients have the misconception that, because herbs are "natural,"
there are no adverse effects. Physicians often do not question patients about
herbal supplements, and patients are often reluctant to divulge the use of
these agents for fear of criticism from their physician. It is important that
dermatologists become aware of the most common, as well as the more serious,
effects. This will aid in better education of patients, as well as better
diagnosis of possible fatal sequelae.
Herbal therapies vary greatly in their therapeutic indexes. For example,
some are consumed as foods and have high therapeutic indexes, and others are
highly biologically active and must be used very carefully. Safety of the
herbs mentioned in this article were addressed in each section, and further
discussion of interactions of herbal therapies that may be encountered in
the dermatologic setting follows.
Many cutaneous reactions to herbal preparations have been reported.
The most common cutaneous adverse effect of herbal preparations is allergic
contact dermatitis. However, more serious cutaneous reactions have been reported.
Two patients developed erythroderma after using topical herbal treatments
for psoriasis and atopic dermatitis, and 1 patient developed Stevens-Johnson
syndrome after taking "Golden Health Blood Purifying Tablets," which contained
multiple herbs, including red clover, burdock, queen's delight, poke root,
prickly ash, sassafras bark, and Passiflora.83 There have been reports of bullous and nodular lichen
planus induced by ingestion of native African medicines.84
A young woman has also been described with leukemia-related Sweet syndrome
elicited by pathergy to topical arnica cream.85
Serious systemic adverse effects have been reported with the use of
CHM for the treatment of dermatologic disorders. The most common are hepatotoxic
effects. Although most patients recover without serious consequences as long
as the medication is stopped, there have been reports of patients with acute
liver failure and death. There are also reports of renal failure and agranulocytosis.46-48 One patient has been
described with adult respiratory distress syndrome after administration of
a CHM, Kamisyoyo-san, for seborrheic dermatitis.86
Another patient was described with reversible dilated cardiomyopathy after
treatment for her atopic dermatitis with a Chinese herbal tea.87
There are also several reports of Chinese and Indian herbal medicines containing
heavy metals, such as lead, arsenic, and mercury. Prescription medications
have also been found in over-the-counter herbal formulations from other countries.
There are many possible drug interactions with herbs and prescription
medications. The most important in the dermatologic setting are discussed.
The immune-modulating effects of Echinacea, Astragalus, licorice, alfalfa sprouts, vitamin E, and zinc
may decrease the efficacy of corticosteroids and immunosuppressants.88 There are herbs that have been shown to cause hepatitis
and therefore should not be used in combination with such medications as methotrexate.
These include many of the ingredients in the CHM preparations, as well as Echinacea, chaparral, germander, ragwort, and life root.87, 89 Herbs containing gamolenic acid,
such as evening primrose oil, which has been used for dermatitis, psoriasis,
and xerosis, lower the seizure threshold, and therefore dosages of anticonvulsants
may need to be increased.87
In addition to the adverse effects discussed already, patients should
be counseled on the lack of regulation for herbal medicines. There are no
quality-control measures currently in place in the United States to ensure
the purity, concentration, or safety of herbal supplements. Although herb
manufacturers are restricted from making efficacy statements, there are no
regulations on claims for which symptoms these herbs can alleviate. In the
United States, there are also no regulations on which herbs can be restricted
in formulations.90
CONCLUSIONS
The use of alternative medical therapy including herbs is increasing
dramatically in the United States. Many of these herbal therapies have been
used for centuries and show good anecdotal results. A few randomized controlled
trials have also shown promising results in the use of herbal therapies for
the treatment of dermatologic disorders. Other countries, such as Germany,
are now requiring standardization of herbal preparations and making specific
recommendations as to the use and efficacy of herbs in the treatment of disease.
However, much more research is needed. For now, it is important to know what
common herbal alternatives exist and which potential adverse effects can occur
so as to counsel patients more effectively.
AUTHOR INFORMATION
Accepted for publication July 6, 2001.
Corresponding author and reprints: Philip D. Shenefelt, MD, Division
of Dermatology and Cutaneous Surgery, Box 79, Department of Internal Medicine,
College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd,
Tampa, FL 33612 (e-mail: pshenefe{at}hsc.usf.edu).
From the Division of Dermatology and Cutaneous Surgery, University
of South Florida, Tampa.
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