People who have had an allergic reaction to penicillin might believe they need to avoid it for life. But 80 percent of people who have an allergic reaction to penicillin lose their allergy within 10 years, if not exposed to penicillin again in that time period.

People who have had an allergic reaction to penicillin might believe they need to avoid it for life. But 80 percent of people who have an allergic reaction to penicillin lose their allergy within 10 years, if not exposed to penicillin again in that time period.

“Most people who lose their penicillin allergy do not realize it,” said Kristen Eblen, antimicrobial stewardship lead pharmacist at Lake Regional Health System. “As a result, their doctors must prescribe more powerful antibiotics to treat simple infections. This increases their chances of having severe side effects and developing difficult-to-treat infections. For example, patients who report a penicillin allergy are more likely to develop C. difficile, a serious infection causing severe diarrhea and even death. They also are more likely to develop MRSA, a difficult-to-treat infection usually requiring IV antibiotics.”

To help people avoid negative effects, Lake Regional Outpatient Services now provides penicillin skin testing, a safe way to determine if a penicillin allergy is still active.  

Testing usually takes two hours. The skin is pricked and injected with weak solutions of penicillin and observed for a reaction. This may cause discomfort due to itching, but it is not painful. A positive skin reaction is an itchy, red bump that lasts about half an hour, then resolves.

A positive test indicates the person is truly allergic. These people should continue to avoid penicillin.

If the patient completes skin testing without a positive reaction, a single oral dose of full-strength penicillin is commonly given to confirm the patient does not have an allergy. About 3 percent or less of people with a history of penicillin allergy and a negative skin test will still experience an allergic reaction. These reactions are very mild.

If a person has a negative skin test and has no reaction to an oral dose of the antibiotic, no future precautions are necessary. Approximately 90 percent of people will test negative either because they lost the allergy or because they were never truly allergic in the first place. These people can safely take penicillin and related antibiotics.

Penicillin skin testing does not provide any information about certain types of reactions. These include extensive blistering and peeling of the skin (Stevens-Johnson syndrome or toxic epidermal necrolysis), a widespread sunburn-like reaction that later peeled (erythroderma) or a rash composed of small bulls-eyes or target-like spots (erythema multiforme). People with these types of reactions should never again take the medication. A second exposure could cause a severe progressive reaction and even death.

The first step to getting tested is to discuss it with a doctor.

“Your doctor will ask about your penicillin allergy — when it occurred and what symptoms you had,” Eblen said. “If they determine you are a good candidate for this testing, they will issue an order. Getting tested is especially important if you are having an upcoming surgery, are prone to COPD exacerbations or pneumonia, or are frequently prescribed antibiotics.”