Nearly everyone knows someone who says they are allergic to penicillin. Up to 10 percent of people report being allergic to this widely used class of antibiotic, making it the most commonly reported drug allergy. Over time, however, the vast majority of people who once had a severe allergic reaction to penicillin lose sensitivity and can be treated safely with the drug (although 10 percent of individuals will remain allergic).
Understanding penicillin allergies is important for a variety of reasons. For certain conditions, penicillin is the best (or only proven) therapy. Some patients need penicillin because they are allergic to other types of antibiotics. Allergists, experts in the treatment and diagnosis of allergies and asthma, may want to know if childhood allergic reactions persist in their adult patients, to establish more complete medical histories and treatment options.
Penicillin Allergy Symptoms
Mild to moderate allergic reactions to penicillin are common, and symptoms may include any of the following:
Hives (raised, extremely itchy spots that come and go over a period of hours)
Tissue swelling under the skin, typically around the face (also known as angioedema)
A less common but more serious, sudden-onset allergic reaction to penicillin is anaphylaxis, which occurs in highly sensitive patients. Anaphylaxis occurs suddenly, can worsen quickly and can be deadly. Symptoms of anaphylaxis might include not only skin symptoms, but also any of the following:
Tightness in the chest and difficulty breathing
Swelling of the tongue, throat, nose and lips
Dizziness and fainting or loss of consciousness, which can lead to shock and heart failure
These symptoms require immediate attention at the nearest Emergency Room. Epinephrine, the therapy of choice, will be given in this urgent care setting, but should also be self-administered via autoinjector as soon as possible by patients who have already been prescribed and are wisely carrying this device.
Penicillin Allergy Testing and Diagnosis
Our allergy specialists can help you evaluate the safety of taking penicillin.
In addition to assessing your detailed history about a prior allergic reaction to penicillin, our allergist will administer skin tests to determine if a person is or remains allergic to the medication. These tests, which are conducted in an office or a hospital setting, typically take about two to three hours, including the time needed after testing to watch for reactions.
When safely and properly administered, skin tests involve pricking the skin, injecting a weakened form of the drug, and observing the patients reaction. People who pass penicillin skin tests by reacting negatively to the injection are seen as at low risk for an immediate acute reaction to the medication. The allergist might then give these individuals a single, full-strength oral dose to confirm the absence of a penicillin allergy.
Those with positive allergy skin tests should avoid penicillin and be treated with a different antibiotic. If penicillin is recommended, people in some cases can undergo penicillin desensitization to enable them to receive the medication in a controlled manner under the care of an allergist.