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

Abstract and Introduction

Abstract

Botanical extracts and single compounds are increasingly used in cosmetics but also in over-the-counter drugs and food supplements. The focus of the present review is on controlled clinical trials with botanicals in the treatment of acne, inflammatory skin diseases, skin infections, UV-induced skin damage, skin cancer, alopecia, vitiligo, and wounds. Studies with botanical cosmetics and drugs are discussed, as well as studies with botanical food supplements. Experimental research on botanicals was considered to a limited extent when it seemed promising for clinical use in the near future.
In acne therapy, Mahonia, tea tree oil, and Saccharomyces may have the potential to become standard treatments. Mahonia, Hypericum, Glycyrrhiza and some traditional Chinese medicines appear promising for atopic dermatitis. Some plant-derived substances like dithranol and methoxsalen (8-methoxypsoralen) [in combination with UVA] are already accepted as standard treatments in psoriasis; Mahonia and Capsicum (capsaicin) are the next candidates suggested by present evidence. Oral administration and topical application of antioxidant plant extracts (green and black tea, carotenoids, coffee, and many flavonoids from fruits and vegetables) can protect skin from UV-induced erythema, early aging, and irradiation-induced cancer. Hair loss and vitiligo are also traditional fields of application for botanicals.
According to the number and quality of clinical trials with botanicals, the best evidence exists for the treatment of inflammatory skin diseases, i.e. atopic dermatitis and psoriasis. However, many more controlled clinical studies are needed to determine the efficacy and risks of plant-derived products in dermatology. Safety aspects, especially related to sensitization and photodermatitis, have to be taken into account. Therefore, clinicians should not only be informed of the beneficial effects but also the specific adverse effects of botanicals used for dermatologic disorders and cosmetic purposes.

Introduction

The term 'botanicals' subsumes numerous preparations derived from herbs, spices, roots, stems, and other materials of botanical origin. Botanicals are used for therapeutic or cosmetic purposes in the form of fresh plants, dried, or extracted plant material. Botanical medicine is also referred to as herbal medicine, phytotherapy, or phytomedicine. The use of plant extracts and herbs has its origin in ancient times, with the earliest records originating from ancient China and Egypt. However, the use of botanicals in dermatology is widely based on personal experience and tradition, and relatively sparse scientific data are available with regard to the efficacy of botanical extracts in controlled clinical trials.[1]

An increasing number of patients and consumers are asking for plant-based therapeutic products as complementary dermatologic therapy. Botanical therapies are often considered as therapeutic alternatives, as agents of safer choice than conventional therapy, or sometimes even as the only effective therapeutic way left to treat a certain skin disorder. The cosmetic industry is taking a good profit of this trend by introducing plant extracts from herbs, flowers, fruits, and seed oleates into their products, promising a gentler, more organic approach to beauty. Botanical-based cosmetics are greatly accepted by the consumers because they are said to possess the ability to detoxify, hydrate, strengthen, stimulate, relax, and balance the skin and hair. These products with active compounds are collectively referred to as 'cosmeceuticals.'[2] Moreover, some specific ingredients of botanicals such as antioxidants, taken orally on a daily basis, may be efficient in preventing the skin from aging by displaying photoprotective effects. These supplements are referred to as 'nutraceuticals,' a portmanteau of nutrition and pharmaceutical.

Botanical cosmeceuticals are largely unregulated and therefore often lack pharmaceutical quality and evidence of safety and efficacy. In the US, botanical extracts are often distributed as dietary supplements without regulatory requirements for standardization, safety, and efficacy.[3] In contrast, in Germany a regulatory authority known as Commission E has conducted an extensive review of more than 300 botanicals with established traditional use.[4] The level of scientific evidence, reporting of adverse events, and toxicologic data were evaluated and resulted in positive or negative plant monographs. The Commission E monographs together with the European Scientific Cooperative on Phytotherapy (ESCOP) monographs and the monographs of the American Botanical Council (ABC) are often used as a basis for decision making by regulatory authorities in European countries and in the US.[4]

This article mainly reviews the results of controlled clinical studies on botanicals used in dermatology. Plant-derived single compounds already established in dermatologic therapy, such as dithranol, salicylates, or podophyllotoxin, are also discussed (table I). In the following sections, the botanicals are discussed under the dermatologic indications in which they have been studied or would be primarily indicated according to their mode of action (table II).

The published literature was searched between December 2007 and March 2010 in the PubMed database. Keywords such as 'botanicals,' 'phytomedicine,' 'phytotherapy,' 'herbal therapy,' and 'herbalmedicine'were entered, combinedwith 'dermatology' and 'skin.' This combination yielded hits for a few specific skin disorders: 'acne,' 'rosacea,' 'atopic dermatitis,' 'psoriasis,' 'chronic venous insufficiency,' 'skin infections,' 'alopecia,' 'vitiligo,' 'wounds,' and 'skin cancer' but also 'UV-protection' and 'sunscreen.' To give examples, 137 hits were found for the combination of 'herbal therapy' and 'atopic dermatitis,' 107 hits for 'herbal therapy' and 'psoriasis,' and 264 hits for 'herbal therapy' and 'skin infections.' Altogether, 1263 articles were found for all searches.Additionally, 'related articles' proposed by PubMed for the selected citations were systematically searched. From these hits all clinical studies were considered, no matter what quality the study was. However, to provide the reader with information on the quality of the studies, each study was classified according to the levels of evidence (LOE) A–D suggested by the UK National Health Service.[5] In brief, LOE-A is assigned to consistent randomized, controlled clinical trials and cohort studies; LOE-B is assigned to consistent retrospective cohorts, exploratory cohorts, outcomes research, case-control studies, or extrapolations from LOE-A studies; LOE-C is assigned to case series studies or extrapolations from LOE-B studies; and LOE-D is assigned to expert opinions without explicit critical appraisal, or based on physiology, bench research, or first principles. Whenever possible, the LOE was indicated for each study in squared brackets, e.g. [LOE-A].

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