FIXED SOLAR URTICARIA

Background: Three unusual cases of solar urticaria limited to fixed sk in sites are described. Objective: Our objective was to study the clin ical course and several therapeutic regimens for fixed solar urticaria . Methods: Phototesting and in vitro activation of a plasma factor wer e performed. Results: Wheals in a patchy pattern were strictly localiz ed to the same circumscribed skin areas; they were reproducible in the ir pattern and location by irradiation. The action spectra ranged from 320 to 700 nm, 320 to 585 nm, and 400 to 560 nm. In one patient inhib ition was found by wavelengths between 280 and 320 nm. Intradermal inj ection of the patients' plasma activated by in vitro irradiation induc ed wheals only in the affected skin sites. The patients showed a good therapeutic response to H-1-antihistamines or repeated exposures to na tural sunlight. Conclusion: The term fixed solar urticaria is proposed for this peculiar type of solar urticaria.