Selective fixed drug eruption to amoxycillin.

A selective fixed drug eruption to amoxycillin but not other betalactam drugs is reported. Penicillins are the drugs most frequently implicated in immunological adverse reactions. The most important of these are allergic reactions where an IgE-mediated mechanism is well established. Other immunological mechanisms have been described in reactions, such as haemolytic anaemia, serum sickness, drug-induced nephritis, drug fever and contact dermatitis. Fixed drug eruption (FDE) is a type of drug-induced dermatosis, the immunopathogenesis of which remains unknown. FDE is an uncommon reaction to penicillin derivatives, and very few cases have been reported. We present a case of a selective FDE to amoxycillin (AX), with no reaction to other betalactam drugs. Although one similar case has been reported, the reactivity to other penicillin derivatives was not assessed.