It isn’t known why some patients develop penicillin allergies. A penicillin allergy occurs when the body’s immune system mounts an overactive response to penicillin and similar antibiotics. Sometimes an adverse reaction to penicillin is not a true penicillin allergy. An allergic reaction to penicillin may include a rash, or even anaphylaxis. Hives, wheezing, itchy skin, and swollen lips, tongue or face are also penicillin allergy symptoms.
Recent studies have shown that up to 87% of people who think that they have penicillin allergies are not allergic. There is a simple skin test available to determine if someone truly has a penicillin allergy.