This study focuses on penicillin allergy, which is a type of allergic reaction that some people experience when taking penicillin antibiotics. People who have a history of penicillin allergy are often referred to allergy clinics to determine if they truly have an immune system reaction to this medication. The study will use amoxicillin, which is a type of penicillin antibiotic, and compare it to placebo. The purpose of the study is to find out whether giving amoxicillin for five days is better than giving it as a single dose for determining if someone has a true immune-mediated allergy to penicillin.
Participants in this study will be people who have a history of delayed allergic reactions to penicillin, meaning their symptoms appeared more than six hours after taking the medication, or people who are unsure about when their reaction occurred. All participants will first receive a single test dose of amoxicillin. Those who tolerate this first dose without problems will then be randomly assigned to receive either amoxicillin capsules or placebo capsules for five days. Neither the participants nor the doctors will know which treatment each person is receiving during the study.
The study will monitor participants for any allergic reactions that occur up to seven days after the first test dose, with additional monitoring continuing up to fourteen days. Participants will have follow-up appointments either through telehealth or in person at the clinic. An independent panel of experts who do not know which treatment participants received will review any reactions to determine if they are truly immune-mediated allergic reactions. The study will also measure how the testing affects participants’ quality of life using a questionnaire at the beginning of the study and again at ninety days.
Belgium 
Denmark 