Phototesting has been performed in 6 atopic patients who had been suffering of eczematous lesions on sun exposed areas. MED was always of normal value. Phototest was positive in 2 patients. Above all photopatch-test with chlorpromazine was positive in 5 out of 6 patients, allowing the diagnostic of persistent light reaction. The cause of photosensitivity may be the use of phenothiazin derivatives anti-histaminic drugs. The use of phenothiazin derivatives has to be avoided in the treatment of atopic condition for this reason and because of the potential risk of actinic reticuloid in the course of persistent light reaction.