LAUSR

(Fig. 1h). Powder-hair products were diffusely distributed and developed as irregular stains (Fig. 1i). Our analysis and the experiment highlighted the association between the types of hair colour products and their pattern of distribution and staining. Fibre dyes were strongly associated with broken hairs and sometimes with short vellus hairs, while liquid and powder types were more likely to result in irregular staining. Given that the majority of patients had FPHL/AGA, the increased number of hair ostias without terminal hairs might have allowed the dye to penetrate the follicles easily and produce follicular signs. However, as the hair dyes also stained intrafollicular spaces, caution should be noted regardless of the underlying disease. Careful history-taking and enquiry about hair products before and during the medical examination would be useful to exclude pseudotrichoscopic signs.