A review on potential herbal treatments for ‘dandruff’ the embarrassing scalp disorder

reshani.kaumada94@gmail.com Abstract Dandruff is a scalp disorder that is characterized by itching, and abnormal and rapid turnover of the outermost layer of the skin of the scalp. The fungi of the genus Malassezia are responsible for causing dandruff. Several herbal remedies have been in use since ancient times for curing dandruff. The effectiveness of herbal extracts and their formulations against the fungi causing dandruff has been assessed previously. This review summarizes the findings of the studies which were focused on assessing the anti-dandruff effect of medicinal plants that are commonly available in Sri Lanka. Punica granatum, Mentha piperita, Bacopa monnieri, Asparagus racemosu s , Azadirachta indica, Elaeocarpus serratus, Psidium guajava, Trigonella foenum-graecum, Cuminum cyminum, and Hibiscus spp. have been shown to be having in-vitro anti-malassezial action. However, the number of clinical trials done on assessing such effects of herbal preparations are limited, and the knowledge generated through the clinical trials hitherto shows that the use of combined preparations of plant extracts are successful in treating dandruff compared to single herb


Introduction
Dandruff is a scalp disorder characterized by itching and abnormal and rapid turnover of the outermost layer of the human scalp. The dead skin is usually released as patches and flakes of greyish-white colour (1). Dandruff and Seborrheic Dermatitis (SD) are the continuations of the same condition that affect skin areas with high sebum secretion. Dandruff is restricted to the scalp and involves itchy, flaking skin without visible inflammation. SD affects the scalp and other seborrheic areas and involves itchy and flaking or scaling skin, inflammation, and pruritus (2). Three main factors encourage the formation of dandruff. They are fungal infections of the scalp, sebaceous secretions, and individual sensitivity to various chemical substances (3). The most widely accepted microbial organism is the lipophilic yeast which belongs to the genus Malassezia. M. restricta and M. globosa are the commonest species causing dandruff (4,5). Clinical symptoms associated with dandruff are skin flaking, pruritus, irritation, and the feeling of a dry or tight scalp. Loosely adherent, small white or grey flakes are characteristic of dandruff, whereas seborrheic dermatitis presents with yellowish oily scales (6). Though dandruff is not an easily contagious disease or a disease with serious clinical outcomes, it is an embarrassing condition that may affect self-confidence and even lead to psychological disturbances in more severe stages (2).

Usual anti-dandruff treatments
Active ingredients used in anti-dandruff medications include keratinolytic agents and antimicrobial agents. Salicylic acid, sulfur, and tar are the main keratinolytic agents used in dandruff treatment, while selenium sulfide, imidazole, flavonoids, phenolic acids, saponins, and hydroxypyridones are the key chemical constituents effective in treating dandruff (7). Table 01 shows the commonly used therapies for dandruff, which have been proven to be effective by in-vitro and/or clinical studies. Apart from those scientifically accepted medications, hundreds of commercial products in the form of shampoo, cream, scalp lotions are being sold and advertised worldwide. Some of them are claimed to contain 'anti-dandruff herbs', despite non-availability of research evidence (8). Furthermore, there are many herbal treatments in the form of home remedies used by people over many years. Some of the herbal preparations have been tested, and significant anti-dandruff effects were reported in the literature. Evaluation of the in-vitro anti-malassezial effect is based on the demonstration of the zone of inhibition around a disk soaked with the aqueous or alcoholic extract of the herbal plant material under evaluation (9). In this review, we have summarized the publications that have described the anti-dandruff and/or anti-malassezial effects of various herbal preparations, which are commonly available in Sri Lanka.  (16) have demonstrated that the chemical constituents in Punica inhibits pro-inflammatory cytokines. Furthermore, it has been shown that Punica granatum has anti-inflammatory, anti-itching, anti-dandruff and anti-oxidant properties (17,18). In a clinical trial done in 2014 in Iran (19), a herbal shampoo prepared with methanol extract of flowers of Punica granatum in combination with other six medicinal plants, Rosmarinus officinalis, Matricaria chamomilla, Urtica dioica, Mentha piperita, Salvia officinalis, and Pirocton olamine had shown effectiveness on dandruff removal, with fewer side effects (19).

Mentha piperita (English: Peppermint, Sinhala: Minchi, Tamil: Pudina)
Mentha piperita is a plant of the family Labiate, which is widespread across the world while mainly found in Europe. Some flavonoids in Mentha piperita leaves, such as menthoside rosmarinic acid and tannins, can inhibit bacterial, fungal, and yeast growth (20). An Iranian research group has observed significant antimalassezial effects of essential oils made up of Mentha piperita (19).

Bacopa monnieri (English: Waterhyssop, Sinhala: Lunuwila, Tamil: Nīrppirami)
Phytochemical analysis of Bacopa monnieri leaves has revealed the presence of tannin, saponin, steroids, flavonoids, phenol, and alkaloids, which are known chemicals to have anti-dandruff effects (21). Crude aqueous and ethanoic extracts of B. monniera have been tested for the antifungal effects against the dermatophytic fungi. In the results of that study, both ethanoic extract and aqueous extracts had high inhibitory action against the studied dermatophytic fungus (22). The leaf extracts of Trigonella foenumgraecum have been found to have an antifungal effect in a study in India (28). Aqueous preparation of germinated fenugreek seeds has been able to produce a zone of inhibition in Malassezia growth, suggesting the possibility of using it as an anti-dandruff agent.

Cuminum cyminum (English: Cumin; Sinhala: Sooduru, Tamil: Cīrakam)
Essential oil prepared with Cuminum cyminum seeds has shown inhibition zones larger in size than the antifungal medication ketoconazole when tested against Malassezia spp. (19). Furthermore, cumin is known to consist of anti-allergic and anti-inflammatory properties, which may contribute to the beneficial effects as a potential herbal treatment against dandruff (29 (27), in their clinical study done in Sri Lanka testing the efficacy of a paste made with leaves of Elaeocarpus serratus (veralu) and Psidium guajava (pera), which are in traditional medicine as a home remedy for dandruff in Sri Lanka, has reported promising results with remarkable symptomatic improvement and complete control of dandruff, with minimum adverse effects (34). Since the authors have not described the preparation of the tested product in detail, the reproducibility of such a result is somewhat questionable. However, we believe further evaluations of such preparation for product development will be worthwhile.
In conclusion, the aqueous and ethanoic extracts of herbs that have demonstrated anti-Malassezia effects in invitro tests include several commonly available plants in Sri Lanka. As some of these are traditional home remedies are already in use for years, the development of commercial products after establishing proper scientific clinical evidence should be encouraged.