Transepidermal UV Radiation of Human Scalp Skin Induces Distinctive Hair Follicle Damage, Mitigated by Topical Caffeine Treatment

The study from 2019 examined the impact of ultraviolet radiation (UVR) on human scalp hair follicles and the protective role of caffeine. It was found that UVR exposure led to significant damage to the hair follicles, including cytotoxicity, DNA damage, reduced cell proliferation, increased cell death, accelerated transition to the catagen (regression) phase, changes in growth factor levels, and mast cell degranulation. The severity of damage increased with higher UVR doses and affected deeper layers of the hair follicles. However, the application of 0.1% caffeine was shown to be non-toxic to skin and hair follicles and even stimulated IGF-1 expression. Crucially, caffeine treatment protected against the cytotoxic and apoptotic effects of UVR and moderated the increase in TGFB2 expression, indicating its potential as a protective agent against UVR-induced hair follicle damage.