Detection of patients with multiple drug allergy syndrome by elective tolerance tests

Background: Multiple drug allergy syndrome (MDAS) caused by antibiotics is frequently observed in allergy departments; however, risk factors for such a condition as well as the means to detect patients prone to MDAS are poorly defined. Objective: The identification of patients prone to MDAS and the detection of risk factors for multiple antibiotic sensitivity. Methods: Two hundred fifty-three elective oral challenges with alternative antimicrobial drugs were performed in 120 patients with histories of recent allergic reactions to antibiotics. Results: Twenty-three (19%) subjects reacted to at least one antibiotic class. All reactions were mild and easily controlled by conventional therapy. Female sex, history of multiple antibiotic reactions, and reactions to nonsteroidal antinflammatory drugs were the main risk factors for reactions to alternative antibiotics. To date, no patient has reported immediate adverse reactions to drugs negative on oral challenge tests but one had urticaria/angioedema on the fifth day of full dose treatment with ofloxacin. Conclusions: Elective oral challenges with alternative antibiotics are a sensitive, specific, and safe means to detect patients with MDAS, thus sparing them more severe adverse reactions caused by full dose therapies. The recommendation to perform oral challenge tests with antibiotics just before their therapeutic use seems unnecessary and should be reconsidered.