Frontal fibrosing alopecia, usually shortened to FFA, is a scarring type of hair loss. It mostly shows up along the front hairline, it mostly affects women after menopause, and once the inflammation has done its damage, the hair in that area does not come back. Sunscreens and cosmetics keep coming up in the research as possible players, so dermatologists in ten hospital departments across Spain patch tested 133 people with FFA. Patch testing means placing small amounts of common allergens on the skin and watching for which ones cause a reaction. Of those 133 patients, 58 percent reacted to at least one allergen in the standard series. People without FFA who were patch tested at the same clinics over the same period reacted at a rate of 52.3 percent, and the researchers found no meaningful difference between the two groups. Three specific allergens did show up more often in the FFA group: propolis, a resin made by bees, shellac, and a group of compounds called gallates. The authors could only connect those reactions to something in the patient's everyday exposure in a minority of cases, so what they mean is still an open question.

Salicylates, ingredients the authors note are common in perfumes, hair cosmetics and sunscreens, caused reactions in 13 patients, just under 10 percent. Those patients were significantly more likely to say that sunscreen or sun exposure bothered their skin. Nearly three out of four patients used sunscreen daily or almost daily, yet frequent sunscreen use was not linked to being sensitized to sunscreen ingredients. Then came the question everyone wants answered. At least four months after testing, patients who were told to avoid their allergens and did so reported no significant improvement in itching, scalp pain or hair loss progression compared with patients who did not avoid them. The authors conclude there is not enough evidence to patch test every FFA patient as a routine step, though testing that includes salicylates may be worth offering to patients who report reactions to sunscreen or the sun. They are open about the limits. The study was done only in Spain, and allergens vary by region. The comparison group was people already referred for patch testing rather than the general public. Salicylates were never tested in that comparison group, so it is still unknown whether those reactions are more common in FFA. The follow up relied on patient questionnaires over a short window, and the authors say improvement is unlikely to show up that quickly. And the study was not designed to show that any allergen causes or worsens FFA.

Here's the study: Pastor-Nieto MA, Gatica Ortega ME, Giménez-Arnau AM, et al. Contact Sensitization in Patients With Frontal Fibrosing Alopecia: Patch Test Results With an Extended Baseline Series in Consecutive Patients. Contact Dermatitis, 2026;95(2):192-199. doi:10.1111/cod.70152. Read the full text here.

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