Botanicals in Dermatology: An Evidence-based Review

Juliane Reuter; Irmgard Merfort; Christoph M. Schempp

Disclosures

Am J Clin Dermatol. 2010;11(4):247-267. 

In This Article

1. Acne

Traditional phytomedicines play an adjuvant role in acne therapy in Europe, in addition to or in combination with intensive cosmetic care. A large number of herbs with antiinflammatory, antihidrotic, and/or antibacterial compounds are used for washing or steambaths. Examples are chamomile (Matricaria recutita), marigold (Calendula officinalis), and wheat bran (Triticum aestivum).[6] After cleaning, creams or aqueous decoctions with astringent compounds like tannins are applied topically. Witch hazel (Hamamelis virginiana) bark extract is most commonly used since it is considered to be very safe in topical administration. Other tannin-containing plants include white oak bark (Quercus alba), English walnut leaf (Juglans regia), agrimony (Agrimonia eupatoria), goldenrod (Solidago virgaurea), jambolan bark (Syzygium cuminum), Labrador tea (Ledum latifolium), lady's mantle (Alchemillamollis), lavender (Lavandula angustifolia), mullein (Verbascumthapsus), rhatany (Krameria triandra), Chinese rhubarb (Rheum palmatum), St John's wort (Hypericum perforatum), and yellow dock (Rumex crispus)[7] [LOE-D]. Other herbs traditionally used topically or as depurative teas are daisy (Bellis perennis), pansy (Viola tricolor), quitch (Elymus repens), and dandelion (Taraxacum officinale).[6] Horsetail (Equisetum spp.) tea is recommended because of its high content of silicic acid, and topical application of yellow milk from fresh leaves of aloe (Aloe ferox) for its anthranoids [LOE-D].

Vitex (Vitex agnus-castus) taken orally has been shown to be effective in the treatment of premenstrual acne [LOE-D].[8] The whole fruit extract increases progesterone levels and decreases estrogen levels by acting upon follicle-stimulating hormone and luteinizing hormone levels in the pituitary gland, and decreases exceedingly high premenstrual prolactin levels via dopaminergic mechanisms.[9] The German Commission E has recommended an intake of 40 mg/day for the treatment of acne.[4] The agent should not be taken by pregnant or nursing women and adverse effects, such as gastrointestinal tract upset and skin rashes, are reported.[8]

Besides the traditionally used antiacne botanicals, several herbs have been investigated for antimicrobial activities to evaluate their potential as herbal therapeutics for acne. Propionibacterium acnes, an anaerobic pathogen, plays an important role in the pathogenesis of acne and seems to initiate the inflammatory process by triggering the release of reactive oxygen species and proinflammatory cytokines[10] [LOE-D]. Interestingly, the pronounced antibacterial effect of licorice (Glycyrrhiza glabra) against P. acnes in vitro is not associated with induction of bacterial resistance[11] [LOE-D]. A recent screening of plant extracts for antimicrobial activity against bacteria and yeasts with dermatologic relevance revealed a strong inhibitory effect on P. acnes of usnic acid, the major constituent of beard lichen (Usnea barbata). Bacterial growth was inhibited at concentrations from 1 μg/mL upwards. Moreover, U. barbata displays antioxidative and broad antimicrobial properties, making it a promising agent for the treatment of acne[12] [LOE-D]. A 4-week open-label clinical trial compared essential oil from basil (Ocimum gratissimum) in four different concentrations (0.5–5%) and in four different bases with placebo and standard therapy (benzoyl peroxide 10%).[13]O. gratissimum essential oil 2%in hydrophilic (alcohol or cetomacrogol) bases reduced lesions faster than standard therapy and was well tolerated, while the 5%concentration was also highly effective but irritating. Although 126 students were included in the patient population, the number of treatment groups was too high for valid statistical proof of efficacy[13] [LOE-B]. Because of their antimicrobial effects, the German Commission E has also approved topically administered bittersweet nightshade (Solanum dulcamara) and systemically administered brewer's yeast (Saccharomyces cerevisiae) in the treatment of acne[8] [LOE-D]. Topical duckweed (Lemna minor) is used in China to treat acne[8] [LOE-D].

Oregon grape root (Mahonia aquifolium or Berberis aquifolium) is used for chronic skin eruptions or rashes associated with pustules in Western traditional medicine as well as in the Japanese Kampo medicines (Japanese traditional herbal medicines based on combinations of a number of individual medicinal plants). The main constituents of the crude Mahonia extract are the two protoberberine alkaloids berberine and jatrorrhizine, which display antimicrobial activity against various strains of coagulase-negative staphylococci, P. acnes, and Candida spp. in vitro[14] [LOE-D]. It has been recently shown in an animal model that berberine 100 μmol/L suppresses sebaceous gland lipogenesis by 63%[15] [LOE-D]. The alkaloid berberine is a bitter substance that displays antiadipogenic and anti-inflammatory effects on 3T3-L1 adipocytes, and the anti-adipogenic effect seems to be due to the downregulation of adipogenic enzymes and transcription factors[16] [LOE-D]. However, the exact mode of action of berberine and berberinerich botanicals in acne is still unknown.

The volatile oilof tea tree (Melaleuca alternifolia), a traditional herbal remedy of the Australian aborigines for bruises and skin infections, might also be beneficial in the treatment of acne. Besides its well known antimicrobial properties, tea tree oil displays anti-inflammatory activities by reducing histamine-induced inflammation of the skin[17] [LOE-D]. In a 3-month, single-blind clinical trial with 124 patients, both tea tree oil 5% and benzoyl peroxide 5% ameliorated acne, although the onset of action was slower for tea tree oil; however, fewer patients in the tea tree oil group reported skin discomfort[18] [LOE-B]. While a placebo group was missing in this older report, recently a 45-day randomized, double-blind, placebo-controlled study with 60 patients has proven the efficacy of topical tea tree oil 5% gel in mild to moderate acne vulgaris.[19] Tea tree oil gel was 3.55-fold more effective than placebo in terms of the total acne lesions count and 5.75-fold more effective in the acne severity index[19] [LOE-A]. Although the study provided no evidence for differences in adverse effects and tolerability, the sensitizing potential of tea tree oil and oxidized monoterpenes should be taken into account when using tea tree oil for the treatment of acne[20] [LOE-C].

Gluconolactone is formed from a polyhydroxy acid synthesized by Saccharomyces bulderi[21] [LOE-D]. The results of a 150-patient, double-blind clinical study with topical application of gluconolactone 14% solution demonstrated a clearance of inflamed acne lesions that was significantly superior to placebo and comparable to benzoyl peroxide 5% but with fewer adverse effects[22] [LOE-A].

1.1 Summary

Traditional herbal treatment in combination with cosmetic care is a well established basis of acne therapy. Some botanicals, especially Oregon grape root, tea tree oil, Saccharomyces, and perhaps basil may have the potential to replace standard chemical therapy in mild to moderate cases because of their good efficacy and higher tolerability. Further valid, controlled clinical studies that also consider optimization of pharmaceutical preparations are needed.

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