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Causes
By Mayo Clinic staffPenicillin allergy occurs when your immune system responds to the drug as if it were a harmful substance instead of a helpful remedy. Your immune system triggers certain cells to produce immunoglobulin E (IgE) antibodies to fight the component of penicillin to which you're allergic (allergen). Chemicals released by your immune cells can cause the signs and symptoms associated with an allergic reaction.
Penicillin belongs to a family of drugs called beta-lactam antibiotics. These drugs include penicillin and amoxicillin, which are relatively inexpensive and effective at treating many common bacterial infections. Such infections include skin, ear, sinus and upper respiratory infections.
Taken orally or injected, penicillin works by stopping the growth of bacteria in your body. Several varieties of penicillin exist, and each targets a different infection in a different part of your body. You may have heard of some of the other drugs in the penicillin family, including:
- Amoxicillin
- Ampicillin
- Dicloxacillin
- Penicillin G
- Penicillin V
- Piperacillin and tazobactam (Zosyn)
If you're allergic to one type of penicillin, you're at risk of being allergic to all penicillin-related antibiotics. Some people allergic to penicillin may also be allergic to cephalosporins, a class of antibiotics closely related to penicillin.
You aren't born allergic to penicillin, but you can develop penicillin allergy once you've been exposed to the drug. After that, re-exposure to penicillin or related antibiotics can trigger an allergic reaction, sometimes more severe than the reaction to the first exposure.
- Yates A. Management of patients with a history of allergy to beta-lactam antibiotics. The American Journal of Medicine. 2008;121:572.
- Solensky R. Allergy to penicillins. http://www.uptodate.com/home/index.html. Accessed Sept. 15, 2009.
- Karabus S, et al. Penicillin allergy in children. Current Allergy & Clinical Immunology. 2009;22:64.
- Solensky R. Patient information: Allergy to penicillin and related antibiotics. http://www.uptodate.com/home/index.html. Accessed Sept. 24, 2009.
- Inamdar R, et al. Penicillin hypersensitivity. American Academy of Allergy Asthma & Immunology. http://www.aaaai.org/members/allied_health/articlesofinterest/penicillin.stm. Accessed September 24, 2009.
- Pegler S, et al. In patients allergic to penicillin, consider second and third generation cephalosporins for life threatening infections. British Medical Journal. 2007;335:991.
