An allergy to penicillin (or another penicillin-related drug) is one of the most common drug allergies. Penicillin allergy typically produces a pink rash, which may vary from flat and not itchy to one that is raised and itchy (hives).

But it also can lead to a severe allergic reaction called anaphylaxis. Symptoms are dizziness, low blood pressure and difficulty breathing. Anaphylaxis can be fatal if untreated.

A penicillin reaction is unpredictable and can occur early or late in a course of treatment. Once someone has had a reaction to penicillin, he or she is more likely to have a reaction to other drugs in the penicillin family (such as amoxicillin, ampicillin or dicloxacillin).

Penicillin allergy can appear at any age, and can run in families. Researchers think that children may require repeated exposure to develop sensitivity. Children with frequent antibiotic exposures, such as those with cystic fibrosis, are more likely to develop a drug allergy.

If your child has had an anaphylactic reaction to penicillin (or any medication, insect bite or food), he or she should wear a MedicAlert or other medical identification bracelet or necklace. Ask your child's health care provider about prescribing self-injectable epinephrine, a medication used to treat anaphylaxis.