The aim of the study was to give a survey of the possible phototoxic reactions of isotretinoin in the Estonian climate.
Subjects and methods. The study was carried out in 10 centres all over Estonia and 96 patients participated in it. The study lasted from April to September 2005, in the period of maximal (over 6) values of UV indices describing strong solar radiation. Maximal UV indices were measured and obtained from the Institute of Estonian Meteorology and Hydrology.
The inclusion criteria were serious or drug resistant acne, signed informed consent, cooperativeness, absence of mental disorders and alcohol abuse, normal laboratory results, absence of pregnancy and effective contraception, no preceding skin reactions to sun’s radiation, washout time from previous treatment one week and patient’s agreement to use the sun protective spray with a factor of 30. Once a month (the length of the treatment course was 4–6 months), the patient was to visit the doctor, who documented the dosage, the side effects of treatment and the regularity of using protection against sun’s radiation.
Results. Phototoxic reactions resembling sunburn occurred in 4.3% of the patients, which is less than described earlier in Europe (5–12%). It is important to distinguish facial erythema from photosensitivity reactions whose common occurrence is 67%.
Conclusion. Care should be taken to avoid overexposure to sunlight in all patients. Patients should be encouraged to apply non-alcohol based non-greasy sunscreen over the summer months or when spending significant periods of time in the sunlight, e.g. during skiing.