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Background Dandruff is a common scalp condition characterized by flakes, pruritus and sometimes mild erythema. These symptoms reflect underlying histopathologic and biochemical events that must be reversed if treatment is to be effective. Objectives This study aimed to better characterize the state of the epidermis in dandruff and to determine how a defined set of skin surface biomarkers of this state change during a successful course of treatment with a potentiated zinc pyrithione (ZPT) shampoo. Methods A population of dandruff sufferers was treated for 3 weeks with a commercial ZPT shampoo or a non-medicated product, and the effect of treatment on adherent scalp flake (ASF) scores was evaluated. Biopsies were taken from lesional sites at baseline and at the end of the study for histomorphometric and histopathologic analysis. Stratum corneum (SC) samples were likewise obtained for evaluation of biochemical markers of inflammation (IL-1α, IL-1RA, IL-8) and barrier integrity (keratin 1, 10, 11; involucrin; SC lipids; human serum albumin). The biomarker profile was evaluated first by comparison with that in non-dandruff subjects at baseline, and then to determine whether any treatment-induced changes were correlated with reductions in flaking in dandruff sufferers. Results Taken together, our studies showed that treatment with the ZPT shampoo led to an improvement in the overall scalp condition as assessed by the resolution of flaking, reduction in epidermal thickness and inflammatory biomarkers, and a dramatic improvement in biomarkers of epidermal barrier integrity. Conclusions The combination of biomarkers examined appears to be a good overall descriptor of the health of the scalp in dandruff, and changes in these biomarkers track with tissue-level events that underlie clinical efficacy in the treatment of dandruff by ZPT shampoo. For the first time, we demonstrate a set of tools that extend beyond flaking scores to provide insight into specific biological changes occurring on the scalp to enable an objective assessment of scalp health.

Background Scalp seborrheic dermatitis and dandruff (SD/D) are chronic conditions requiring long-term treatment. There is a common belief that patients frequently experience decreasing benefits over time when using a single product. This physiologic accommodation is termed tachyphylaxis. Aim To systematically investigate the anecdotal belief that tachyphylaxis occurs in long-term treatment of SD/D using quantitative clinical assessments. Methods An international questionnaire completed by 722 dermatologists assessed the belief of tachyphylaxis incidence with pyrithione zinc (PTZ)-based shampoos, time course, occurrence relative to active ingredients, and effect of switching products. Two double-blind, randomized, clinical evaluations were conducted, 24- and 48-week studies, whereby a 1% PTZ shampoo, a 2% PTZ shampoo, or a matched placebo control shampoo was used by each subject for the duration of the study. Dermatologists assessed the adherent scalp flaking (scale of 0–10) at baseline and at specified intervals. Results Sixty-four per cent of responding dermatologists believed tachyphylaxis occurred with PTZ products, and most felt that tachyphylaxis occurred within 3 months of use. Evaluation of mean treatment responses vs. placebo and individual responses as a function of study duration showed a consistent benefit for all products at all time points; therefore, no evidence for tachyphylaxis was found (within 48 weeks of treatment). Conclusion No evidence for tachyphylaxis in SD/D treatment by PTZ-based shampoos was found. Compliance could explain the decreasing response rate seen over time; the solution is to choose an affordable therapeutic product that is effective long term without cosmetic trade-offs.