Beta-lactam antibiotics include penicillin and cephalosporins and are among the most prescribed antibiotics. This category of drugs is the most involved in immediate allergic manifestations with 2% reactions in treated subjects and a fatal outcome in 1/50000 treatments. Reactions are IgE-mediated and have a considerable but unknown genetic origin, revealed by studies in groups of different ethnical origins in the same geographical region. There are also some families with a high frequency of allergic reactions without identified Mendelian inheritance.

The purpose of this study is to identify predictive risk factors associated to immediate allergic reactions against beta-lactam antibiotics with a pangenomic approach.

A secondary purpose is to identify rare predictive factors with homozygosity mapping and exome sequencing in various families with high risk of allergy to beta-lactam antibiotics.

Inclusion Criteria:

• Informed consent
• Allergy group: Immediate allergic reaction (less than 2 hours after drug administration) to an antibiotic of penicillin or cephalosporin groups
• Allergy group: Positive skin test (intradermal test) with a non-irritant dilution of antibiotic of penicillin or cephalosporin groups

Exclusion Criteria:

• Refusal of participation

Population having an immediate IgE-mediated hypersensibility to beta-lactam antibiotics and matched control subjects.