Background: Allergic reactions to drugs constitute one of the most frequent reasons for consultations in Allergology services with an increasing prevalence in recent years.
Objectives: To describe the results of the Alergológica-2005 study on the clinical characteristics of patients consulting for suspected drug allergies.

Methods: Alergológica-2005 was a descriptive, cross-sectional, prospective, observational study undertaken with 4991 patients treated for the first time in Allergology services in Spain.

Results: Seven hundred thirty-two patients (mean age 41.4 ± 19.4 years) presented for drug allergies (62% females, 38% males). Diagnosis was confi rmed in 26.6% of cases and rejected in 37.2%. Seventy fi ve percent reported only cutaneous symptoms and 10% anaphylaxis. Forty-seven percent of reactions were caused by ß-lactams (63% of which were due to amoxicillin), 29% by nonsteroidal anti-inflammatory drugs (NSAIDs) and 10% by pyrazolones. Sixty nine children were treated for this reason, 8 of whom were diagnosed as drug allergic (5 to ß-lactams, 2 to NSAIDs and 1 to pyrazolones).

Conclusions: Drug allergies are the third most important reason behind consultations in Allergology services, after bronchial asthma and rhinitis. Females are predominantly affected and the ß-lactams, NSAIDs and pyrazolones are the 3 drug families most responsible.

Key words: Drug hypersensitivity. Epidemiology.