Penicillin is one of the earliest discovered antibiotics and a drug of choice for several infections. Up to 10 to 20% of all patients in clinical trial are labeled as penicillin allergic. Most of these patients do not have a true allergy but few have had it verified. Approximately 80% of patients with IgE-mediated penicillin allergy lose their sensitivity after 10 years. Several studies have been conducted denying the risk of sensitization following negative testing of penicillin allergy. Investigators have not had the same experience and have therefore decided to conduct a retrospective study review of 83 adult outpatients with a distant penicillin allergy label and evaluate outcomes of skin retesting six weeks following Drug Provocation Test and challenge.

Inclusion Criteria:

- 18 years old

Exclusion Criteria:

• Pregnancy
• poorly controlled asthma and cardiovascular disease
• use of drugs that interfere with testing and could not be stopped such as antihistamines, tricyclic antidepressants, antipsychotics, beta blockers, high dose oral glucocorticoids
• Non-IgE mediated type of serious allergic reaction such as Stevens - Johnson syndrome, Toxic Epidermal Necrolysis, and Drug Rash with Eosinophilia and Systemic Symptoms (DRESS) Syndrome.

Patients were recruited during the clinical evaluation of labelled penicillin allergy at the regional hospital of Metz, France (Mercy, Centre Hospitalier Régional CHR de Metz - Thioville). All patients were well and had no need of penicillin treatment at the time of evaluation and testing. A detailed history of the probable implicated molecule, the type of the reaction, the age at onset and the received treatment were obtained by Dr SL.