[Quinidine-induced photoallergy. A clinical and experimental study].

Photoallergies are type-IV allergic reactions of a special kind. Photoallergies due to quinidine sulphate were described as early as 1942. We present a case of quinidine sulphate-induced photodermatitis. The photoallergic reaction to quinidine sulphate was reproducible not only after oral intake but also in the photopatch test. In addition, an eczematous dermatitis was provoked after intradermal injection of quinidine sulphate previously exposed to UV-A irradiation in vitro together with serum taken from the patient. No dermatitis was seen with quinidine sulphate irradiated in the absence of serum. The binding of the hapten quinidine sulphate to a potential carrier protein in the serum seems to be of crucial importance in this type of photodermatitis. Quinidine sulphate is frequently used as an antiarrhythmic drug. Its potential photoallergenic action should always be considered.