We present a case of aminophylline hypersensitivity reaction due to ethylenediamine. A thirty-year-old Japanese female admitted to our hospital to evaluate generalized urticarial reaction immediately after intravenous administration of aminophylline. Skin intradermal testing was positive with ethylenediamine. A positive intravenous test was found with aminophylline and negative with diprophylline which does not contain ethylenediamine. There are some reports of aminophylline hypersensitivity reaction and the most cases were delayed type reaction in English literatures. However, most of Japanese cases were immediate type. Acetylation is a main metabolic pathway of ethylenediamine. Most of Japanese have a rapid or intermediate acetylators on the other hand. Caucasian have a 50% likelihood of being slow acetylators. This difference suggest the different incidences of immediate and delayed reaction of aminophylline hypersensitivity reaction in Japanese and Caucasian respectively.
