LAUSR

Using a matched case-control study design, Aldoori et al (2016) report a possible association between frontal fibrosing alopecia (FFA) and the regular use of sunscreens and facial skin care products.1 We commended the authors for drawing attention to potential environmental causes of this disfiguring condition. However, several methodological limitations drew our attention. First, we are concerned about selection bias. Control subjects were selected from hospital staff through advertisements and from friends and family of the authors. Ideally, controls should be randomly sampled from the source population that gave rise to cases. This article is protected by copyright. All rights reserved.