Mask‐Induced Koebner phenomenon and its clinical phenotypes: a multicenter, real‐life study focusing on 873 dermatological consultations during COVID ‐19 pandemics

During COVID-19 pandemic, wearing masks for prevention became mandatory but evidence suggest that is also detrimental for skin. Although facial dermatoses due to masks increase in both healthcare workers and general population, a pathogenetic hypothesis remains still elusive. To evaluate the prevalence of dermatological consultations due to Koebner triggered dermatoses In this prospective, multicenter, real life study carried out in Italy from March 11th to December 11th 2020 during COVID-19 pandemics, we evaluated dermatological consultations (in-person and telemedicine) to study the prevalence of Koebner (KB) phenomenon due to masks. We adopted Boyd and Nelder classification for Koebner phenomenon and Bizzozero's for KB intensity. A total of 229/873 (26.2%) dermatological consultations were KB triggered dermatoses and lesions were located in mask-covered ear area (76 [33.2%]), malar area (73 [31.8%]), perioral area (53 [23.1%]) and nose (27 [11.8%]). First KB category grouped 142 patients (psoriasis, vitiligo, maskne and mask rosacea), second one 24 (warts, molluscum contagiosum and impetigo), third one 46 (atopic dermatitis) and fourth one 17 (eczema). Among previously KB negative psoriatic patients that became KB positive, 9/13 (69.2%) had discontinued or modified prescribed anti-psoriatic treatments. Mask-related Koebner phenomenon is an important clinical sign to orient clinician's therapeutic protocols during COVID-19 pandemic, especially in patients with psoriasis.