Multiple Drug Hypersensitivity Syndrome

Inclusion criteria: * Patients who consulted at our allergy clinic (University Hospital of Montpellier, France) * Between September 1996 and February 2018 with a clinical history suggestive of DHR * Who completed a tailored drug allergy work-up, (including a drug allergy questionnaire, skin tests (STs) and drug provocation tests (DPTs)) and were diagnosed with MDH. Exclusion criteria: * the DHR was due to a single component contained in 2 different drug formulations * in composed drugs; * there was possible cross-reactivity between the responsible drugs; (iv) the patient had positive but non standardized nor validated (i.e. possibly irritant) * these STs were followed by a negative DPT; * DPTs with placebo were positive; (vii) doubtful tests were repeated and eventually considered negative; * a single DHR was associated with one or more non-drug related contact allergies; * DPTs elicited subjective manifestations (i.e., isolated pruritus, headache, isolated abdominal pain); * non-specific histamine release was suspected (e.g., chronic spontaneous - desensitization, rather than a diagnostic work-up was preferred in order to meet the urgent therapeutic needs of individual patients (HIV infected patients, cardiac patients).