2. Evidence Acquisition
Medicinal plants have a long history of use (7) and have been shown to possess low side effects (8, 9). Other than diseases such as common cold and infectious diseases, they have been useful in prevention (10, 11) and treatment (12,13) of a wide variety of diseases that are difficult to cure, such as cancer (14), cardiovascular diseases (15, 16), diabetes (17, 18) hypertension (19, 20) and atherosclerosis (21, 22). Medicinal plants also possess the capacity to diminish drug-induced adverse effects (23, 24) and even heavy metal or other toxicities, such as the protective effect of artichoke (Cynara scolymus) leaf extract against lead toxicity in rats (25). Acne vulgaris drugs mostly possess adverse effects and therefore, medicinal plants might be considered as reliable sources for development of new drugs.
In this paper other than presenting the possible causes of acne vulgaris and its available drugs, recently published papers about medicinal plants used in the treatment of acne vulgaris are reviewed. In this study, we attempted to present information from studies published since early 1980, which were present in databases such as Google scholar, PubMed and Scopus related to medicinal plants effective in the treatment of acne vulgaris. The included key words were phytomedicine, botanicals, herbs, medicinal plants, herbal medicines, herbal therapy or phytotherapy, and acne vulgaris.
Generally, 1176 articles were obtained as the result of the research. Overall, 58 articles including clinical and non-clinical studies were found to be useful and were included in this review.
3.1. Causes of Acne Vulgaris
3.1.1. Infectious Contribution
Staphylococcus aureus and Propionibacterium acnes have been attributed to acne vulgaris. However, their exact contributions in the acne process are not entirely clear. There are sub-strains of P. acnes in normal skin and some others in long-term acne complications. Therefore, it is unclear whether these strains are involved in this condition or they are pathogenically acquired. Resistance of P. acnes to commonly used drugs has been shown to be increasing (1). These strains are able to change, perpetuate, or adapt to the abnormal oil production, inflammation and inadequate sloughing of acne pores. Infection with Demodex, which is a parasitic mite has been shown to be associated with the development of acne. However, eradication of the mites has not improved acnes (26).
3.1.2. Dietary Contribution
The relationship between diet and acne is unclear as there is no good quality evidence. However, a high level of glycemic diet has been shown to be associated with worsening of acne vulgaris. A positive correlation between the use of milk, chocolates or salt, and increase in the severity of acne vulgaris has also been suggested. However, the contribution of chocolates is disputable, as they can be made with different amounts of sugar, with or without milk. A relationship between obesity and acne has also been reported (27).
3.1.3. Genetic Contribution
For specific subjects, the predisposition to acne might be explained by a genetic component. This suggestion has been supported by some studies that have evaluated the rate of acne among first degree relatives, as well as twin studies. There are varieties of genes, which have been attributed to acne, such as polymorphisms in IL-1α, TNF-α, and CYP1A1amongst others (28).
3.1.4. Hormonal Changes
Hormonal changes, such as puberty and menstrual cycles, seem to contribute to formation of acne vulgaris. An increase in some sex hormones, especially in androgens during puberty and pregnancy, cause the follicular glands to produce more sebum. The use of anabolic steroids usually has similar effects. The hormones, which have been attributed to acne vulgaris consist of testosterone, dehydroepiandrosterone and dihydrotestosterone, as well as insulin-like growth factor 1. Development of acne vulgaris in adult women might be due to an underlying condition such as Cushing syndrome, polycystic ovary syndrome or hirsutism (29).
3.1.5. Psychological Contribution
Some scientific researchers have indicated that acne severity is correlated with an increase in stress level and stress has been listed as a factor attributed to acne flare. However, the connection between stress and acne vulgaris has been debated by some other studies (30).
3.2. Medical Treatments
Topical or/and systematic treatments are used to treat acne. The response of patients to treatment is considerably different. Usually more than one treatment modality is employed to treat acne and best results are achieved when treatments are individualized on the basis of clinical evaluations. Retinoids are the mainstay of therapy in patients who only have comedones. They are capable of reducing inflammatory lesions and the number of comedones (40% - 70%). Other agents, including isotretinoin, oral antibiotics, topical antimicrobials, and hormonal therapy, have been shown to yield high response rates. Patients with mild to moderate severity, inflammatory acne with papules and pustules are recommended to be treated with topical antibiotics combined with retinoids. For patients with moderate to severe inflammatory acne, oral antibiotics are the first-line therapy. However, oral isotretinoin is recommended for severe nodular acne, frequent relapses, treatment failures or severe psychological distress. Isotretinoin is the most effective drug and to avoid long-term topical or oral antibiotic therapy, which may cause bacterial resistance, this drug may be recommended. However, isotretinoin is a powerful teratogen, needing strict precaution for use among women of the childbearing age. Medicinal plants are also used for the treatment of acne and are discussed below (1, 31).