According to a Canadian study reported at the annual meeting of the American Academy of Allergy Asthma and Immunology, antibiotics and vaccines are the medicines that most often cause adverse reactions in children. "There is relatively little pediatric data on adverse reactions, which can range from rashes to potentially fatal hypersensitivity". More than 1,500 Canadian cases were reviewed between 1985 and 1995 by Sandra R. Knowles and her colleagues at the Sunnybrook Health Sciences Center in Toronto. In all, 1,800 drugs were implicated in this study.
The leading problems were caused from: Amoxicillin/Ampicillin with a 24% reaction rate, vaccines in general with a 19% reaction rate, Trimethoprim came in with 8%, Sulfamethoxazole (sulfa drug) at 8%, Erythromycin - was at 3%, and Penicillin also at 3% reaction rate.