Anaphylaxis to topically applied sodium fusidate

Fusidic acid is a bacteriostatic antibiotic that is effective primarily on gram-positive bacteria, such as Staphylococcus and Corynebacterium species. It is often topically applied to the skin, but is also given systemically as a tablet or injection. Allergic contact dermatitis, or urticaria, has been reported as a side effect of fusidic acid treatment, whereas anaphylaxis to topically administered fusidic acid has not been reported previously. A 16-year-old boy visited an outpatient clinic for further evaluation of anaphylaxis. He suffered abrasions on his arms during exercise, which were treated with a topical ointment containing sodium fusidate. Within 30 minutes, he developed urticaria and eyelid swelling, followed by a cough and respiratory difficulty. His symptoms were relieved by emergency treatment in a nearby hospital. To investigate the etiology, oral provocation with fusidate was performed. After 125 mg (1/2 tablet) of sodium fusidate was administered, he developed a cough and itching of the throat within 30 minutes, which was followed by chest discomfort and urticaria. Forced expiratory volume in 1 second (FEV1) dropped from 4.09 L at baseline to 3.50 L after challenge, although wheezing was not heard in his chest. After management with an inhaled bronchodilator using a nebulizer, chest discomfort was relieved and FEV1 rose to 3.86 L. The patient was directed not to use fusidate, especially on abrasions. Here we report the first case of anaphylaxis resulting from topical fusidic acid application to abrasions.