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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), |
