Does resistance develop?
Dandruff and its closely related cousin seborrheic dermatitis are often chronic conditions which means that long terms treatments are needed. Anti-dandruff shampoos are typically viewed as first line agents. Many patients raise concerns that chronic use may be associated with development of resistance or some type of decreased benefit if continuously used. The proper term when something does not work as well with continued use is “tachyphylaxis.” So does, continued use of anti-dandruff shampoos give tachyphylaxis?
A 2009 study investigated the anecdotal belief that tachyphylaxis occurs in long-term treatment of seborrheic dermatitis and dandruff. 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. A questionnaire was also sent to dermatologists asking about their views of whether “tachyphylaxis” could really develop or not. Interestingly, Sixty-four per cent of responding dermatologists believed tachyphylaxis occurred with PTZ products, and most felt that tachyphylaxis occurred within 3 months of use. However the actual clinical data showed that there was no evidence for tachyphylaxis within 48 weeks of treatment.
The conclusion from the study was that there was no evidence for tachyphylaxis in the treatment of seborrheic dermatitis and dandruff. It appears the advice many dermatologists give their patients about these agents is opinion based rather than factual.
Schwartz et al. Does tachyphylaxis occur in long-term management of scalp seborrheic dermatitis with pyrithione zinc-based treatments?
Int J Dermatol. 2009.
Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887