Environmental Pathobiology of Frontal Fibrosing Alopecia: Does Linalool Promote FFA Development and Progression by Inducing Epithelial Hair Follicle Stem Cell Damage and MICA Expression in the Bulge?

This study investigates the potential role of linalool, a common allergen in personal care products, in the development and progression of frontal fibrosing alopecia (FFA), particularly in post-menopausal women. The research provides preliminary evidence that exposure to 1% linalool can damage epithelial hair follicle stem cells (eHFSCs) by decreasing their number and K15 expression, without upregulating bulge MHC class Ia expression. Linalool also increases the expression of the "distress" signal MICA, which may activate harmful immune interactions and increase IFNg secretion by CD8+ T cells, contributing to FFA pathogenesis. Additionally, linalool exposure leads to an increase in perifollicular CD68+ macrophages and upregulates MICA expression in non-lesional FFA biopsies, promoting pathological epithelial-mesenchymal transition (EMT) in eHFSCs. These findings suggest that allergens like linalool in personal care products may trigger immune responses that contribute to FFA, indicating that such products should be avoided to prevent FFA progression.