Will my anti-dandruff shampoo stop working if I carry on using it?

Dandruff (D) and its related condition, seborrheic dermatitis (SD) is a long term condition where treatment has to be ongoing to manage it. Anti-dandruff shampoos contain zinc pyrithione (PTZ) are often used to control the condition. One often thinks that with regular use of such shampoos, would they stop working if used for long term?

Research was carried to uncover whether there is a diminished effect (tachyphylaxis) of anti-dandruff shampoos if used for long term. This was published in 2009 in the International Journal of Dermatology.

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.

Prior to the study, sixty-four per cent of responding dermatologists believed that tachyphylaxis occurred with PTZ products if used over a prolonged period of time, and most felt that tachyphylaxis occurred within 3 months of use.

Dermatologists assessed the adherent scalp flaking (scale of 0-10) at baseline and at specified intervals. The results were a contradiction to what the Dermatologists believed.

There was NO evidence that the shampoos stopped being effective in treating SD/D treatment at week 48. Compliance of using the shampoos could explain the decreasing response rate seen over time