Interest of the Second Phase of the Oral Challenge Test in Patients With Suspected Long-standing Penicillin Allergy

The most common drug allergy reported is penicillin allergy, approximately 10% of the world's population. According to the latest studies, only 1-2% of them have a proven hypersensitivity to penicillins. Being wrongly labeled "allergic" leads to a loss of chance for patients to be treated with a molecule of less efficacy than penicillins, an increase in bacterial resistance by broadening the spectrum of action of the molecules prescribed as an alternative and ultimately a additional financial cost. There are several forms of hypersensitivity: the two most classic: immediate hypersensitivity (type I according to Gell and Combs) with a reaction within an hour of taking and non-immediate hypersensitivity with a reaction occurring several days later (type IV according to Gell and Combs). A large majority of patients report a history of allergy in childhood that is poorly described and most often absent from health records. In most cases, this may be a viral rash concomitant with a febrile episode mistakenly mistaken for an allergic skin reaction. Patients are then tested for several decades, in adulthood, after their initial reaction. This latency of time involves a risk of negativation of the allergic tests and it is not excluded that the skin tests or drug reintroductions re cause sensitization to the antibiotic tested and that ultimately the patient reacts when taking the future drug. In fact, it is recommended to optimally explore patients approximately 6 months after an allergic reaction (except for severe drug eruptions).

The exploration of drug hypersensitivity to penicillins therefore involves a strict questioning of the circumstances of the so-called allergic reaction allowing the reaction to be classified as immediate or delayed, then skin tests (prick test, IDR and Patch test according to the immediate profile or delayed) and finally the hospital provocation test. While provocation tests are carried out conventionally most often within one day, it has been shown that some patients react several days after taking penicillin repeatedly: 6.1% have a reaction in their protocol of taking for 5 days at home in the context of a delayed allergy.

In the allergology service at hôpital Paris Saint-Joseph, the protocol corresponds to 2 successive reintroductions.

This study is to evaluate the protocol for reintroducing Amoxicillin or Augmentin carried out over two stages: a first with 100 mg (i.e. 1 / 10th of a dose) then a second with a dose of 1200 mg 1 month later. It would be a question of seeing if with the second reintroduction, one could not catch up with allergic people who would have presented a false negative during the first reintroduction because of explorations too far away from their initial reaction.