In vitro efficacy of antifungal agents alone and in shampoo formulation against dandruff-associated Malassezia spp. and Staphylococcus spp.

Dandruff is a complex skin condition characterized by unpleasant itching and flaking of the scalp. It is primarily attributed to the over colonization of Malassezia yeasts such as Malassezia globosa and Malassezia restricta. Some studies also suggest the involvement of staphylococci bacteria in dandruff disease pathogenesis. We aimed to access the effectiveness of anti-dandruff treatments by determining the efficacy of the active antifungal agents alone or in commercial shampoo formulations against Malassezia and Staphylococcus.

The minimum inhibitory concentrations of three anti-dandruff shampoo antifungals (zinc pyrithione, ketoconazole and ciclopirox) and the witch hazel extract, hamamelitannin were tested against commensal Malassezia and Staphylococcus species using broth microdilution methods. In experiments simulating shampoo exposure and washing conditions on the scalp, we also tested the ability of the above agents in shampoo formulation (Head and Shoulders^® (H&S), Ketomed^® , Sebiprox^® , Erol Healthcare Hair Shampoo^® respectively) along with a generic over-the-shelf shampoo to inhibit microbial growth.

Ketomed^® and H&S shampoo were the most effective treatments against Malassezia in in vitro assays and washing simulation experiments. Erol Healthcare Hair Shampoo^® was less effective against Malassezia as it required a longer contact time to achieve growth inhibition for some species. Sebiprox^® showed variable efficacy in washing and contact time experiments whereas the generic over-the-shelf shampoo was the least effective in inhibiting Malassezia and Staphylococcus growth.

From these findings, it is reasonable that patients with dandruff may benefit from applying specific antifungal shampoo although results may vary with microbial species, time of contact and shampoo formulation components.