Loss of tolerance 5 days after discontinuing sulphonamide introduced via desensitization in delayed reaction.

The fixed drug eruption is a non-immediate hypersensitivity reaction to drug, characterized by recurrent erythematous or violaceous, rounded, well-defined border plaques, which always appear in the same location every time the culprit drug is administered. The usual practice is to avoid the drug involved and to use a structurally different drug. However, there are situations in which there is no safe and effective therapy. In such situations, desensitization is the only option. We describe the case of a patient who presented fixed eruption due to sulfamethoxazole-trimethoprim, who underwent successful desensitization, but required a repeat procedure twice due to relapse after inadvertent full-dose reintroduction. In non-immediate hypersensitivity reaction to drug, the indication is controversial and there is no technical standardization. Furthermore, the time at which such tolerance is lost after discontinuing the drug involved is unknown. In severe non-immediate reactions of types II and III, desensitization is contraindicated. The patient underwent desensitisation to sulfamethoxazole-trimethoprim three times - the first with recurrence of lesions and the second and third without manifestations, all concluded successfully and with no premedication.