Hair loss is a distressing condition that is associated with a multitude of natural, medical, or nutritional conditions. For example, androgenetic alopecia in men, or male pattern baldness, is increasingly recognized as a physically and psychologically serious medical condition that often requires a professional care by generalist clinicians (1).
The only products sanctioned by the US FDA for hair loss treatment are oral finasteride (Proscar®) and topical minoxidil (Rogaine®). Minoxidil was originally created as a hypertension medication by Upjohn Pharmaceuticals (2). Upjohn itself has warned of possible negative side effects of the medication including increased heart rate, difficulty breathing, rapid weight gain, edema, seborrhoeic dermatitis, scalp itching, and scaling (3–5).
Traditional plant remedies have been used for centuries in the treatment for hair loss, but only a few have been scientifically evaluated (5). Peppermint (Mentha piperita) extracted from peppermint leaves is generally regarded as an excellent carminative and gastric stimulant, and also has been used in cosmetic formulations as a fragrance component and a general skin conditioning agent. The principal ingredient of peppermint oil, menthol, is primarily responsible for its beneficial effects (6). In vitro, peppermint has been reported to show anti-inflammatory, antimicrobial, and antifungal activities as well as strong antioxidant activity, and antiallergenic and antitumor actions (7,8). Several clinical trials examining the effects of peppermint oil (PEO) on irritable bowel syndrome have been reported (9). However, experimental trial of PEO in its hair growth activity has not been fully reported. The aim of this study was to address the therapeutic potential of PEO for hair loss via the comparative analysis between PEO and minoxidil.
Hair growth promotion. From week 2, PEO grew hair more rapidly than SA and JO. At week 3, PEO remarkably promoted hair growth than SA and JO, even greater than MXD. At week 4, PEO showed hair growth about 92%, whereas MXD about 55% (Fig. 1).
Hair growth promotion was evaluated by observing the darkening of the skin color, which indicated telogen to anagen conversion, bright pink in telogen and grey/black in anagen. At week 1, PEO changed the dorsal skin color from pink to grey/black and from week 2, it showed a considerably rapid increase in hair growth (Fig. 2). These results clearly demonstrate that the topical application of PEO induces rapid anagen hair growth in telogen mouse skin.
Increase of dermal thickness, hair follicle number and hair follicle depth in histological analysis. Histological analysis showed that 4-wk topical application of PEO and MXD induced very thick and long hair growth and promoted the elongation of hair follicles from dermis to subcutis (Fig. 3). These results indicate that the hair follicles of PEO and MXD groups at week 4 were in the anagen stage. We also observed a slight increase of epidermal thickness in PEO group.
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