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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 creates antibodies to attack the medication. 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
- Nafcillin
- Penicillin V
- Penicillin G
Some people allergic to penicillin may also be allergic to cephalosporins, a class of antibiotics closely related to penicillin. Around 4 percent of those with a known penicillin allergy have an allergic response to these medications.
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.
