Dandruff has an altered stratum corneum ultrastructure that is improved with zinc pyrithione shampoo

Transmission electron microscopy of scalp tape strips indicates that dandruff scalp possesses abnormal stratum corneum (SC) ultrastructure that is normalized by treatment with small-particle zinc pyrithione (ZPT). Similar abnormalities occur throughout the scalp of those with dandruff, even where no flaking is present. SC abnormalities are consistent with hyperproliferation, including parakeratosis, lipid droplets within corneocytes, few desmosomes, corneocyte membrane interdigitation, and excessive disorganized intercellular lipid. Reversal of SC abnormalities would require treatment of the cause(s) of dandruff, not merely flake removal. A protocol was developed to quantify scalp structural abnormalities by scoring cells from scalp tape strips for yeast number, amount of intercellular lipid, normal intercellular lipid structures, prevalence of intracellular lipid droplets, parakeratotic corneocytes, and corneocyte interdigitation. This protocol was used to compare dandruff and normal SC to dandruff SC treated with either commercial ZPT-containing shampoo or a placebo. Treatment with commercial ZPT shampoo significantly returned SC ultrastructure to normal, suggesting control of the cause of dandruff.