Penicillin Allergy

Diagnosis

A careful exam and appropriate diagnostic tests are essential to accurately determine a penicillin allergy. Misdiagnosis may lead to use of ineffective or more expensive antibiotics.

Your healthcare professional will review your medical history, ask about your symptoms, and perform a physical exam. Referral to an allergist may be needed for specialized testing, which can include:

• Skin tests. A small amount of the suspected penicillin is placed on your skin with a tiny needle. A positive reaction results in a raised, itchy, discolored bump. A negative result usually indicates low risk of allergy, though some reactions cannot be detected with skin tests.
• Graded challenge. If allergy status is uncertain, you may receive up to five increasing doses of penicillin under careful monitoring. No reaction at the full dose indicates that you can safely take that antibiotic. For individuals allergic to one type of penicillin, a graded challenge with a different penicillin or cephalosporin may help identify a safe alternative.

Supportive care is available during testing to manage any reactions.

Treatment

Treatment for penicillin allergy includes managing current symptoms and, in certain cases, reducing sensitivity to the antibiotic.

Treating current symptoms
• Withdrawal of the medicine. Stopping penicillin is the first step when an allergy is suspected.
• Antihistamines. These can block the immune response during an allergic reaction. Prescription or over-the-counter options may be used.
• Corticosteroids. Oral or injected corticosteroids may reduce inflammation from more severe reactions.
• Anaphylaxis treatment. Severe reactions require immediate medical attention, including medication and hospital care to support breathing and blood pressure.

Medicine desensitization
If no suitable antibiotic alternatives are available, desensitization may be recommended. This involves starting with a very small dose of penicillin and gradually increasing the dose every 15 to 30 minutes over several hours or days. Successful desensitization allows completion of the antibiotic course.

Patients are closely monitored during desensitization, and supportive care is available. The process must be repeated for future courses of penicillin, and there is a risk of serious reactions.