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 Diseases and Conditions
Penicillin allergy
From MayoClinic.com
Special to CNN.com Introduction Chances are your doctor has at one time or another written a prescription for the antibiotic penicillin for you or a member of your family. It's one of the most frequently prescribed medications, and it's commonly used to treat strep throat and ear infections. But if you have a penicillin allergy, taking this drug can be dangerous. Allergic responses occurring with a penicillin allergy range from annoying rashes to life-threatening reactions, such as difficulty breathing. Penicillin allergy is the most common drug allergy. It isn't clear why some people develop penicillin allergy while others don't. Prevention focuses on awareness. Treating an allergic reaction may require taking medications or, in the case of a serious reaction, emergency care. Signs and symptoms Common signs and symptoms of penicillin allergy include:
Tell your doctor if you notice any of the signs or symptoms of penicillin allergy. He or she can determine if you're having an allergic reaction and may prescribe an alternative medication. The most serious allergic reaction to penicillin is an anaphylactic (an-uh-fuh-LAK-tik) response, which can be deadly. Anaphylactic reactions develop immediately after penicillin exposure in highly sensitive people and cause the airways (bronchi) to constrict, making it difficult to breathe. Blood pressure may drop to life-threatening levels, making you feel dizzy or causing you to lose consciousness. Other serious signs and symptoms include:
Seek emergency medical care if you think you or someone else is having an anaphylactic reaction. Causes Penicillin belongs to a family of drugs called beta-lactam antibiotics. These drugs include penicillin and amoxicillin, which are relatively inexpensive and generally effective at eradicating 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:
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. Penicillin allergy occurs because your immune system responds to the drug as if it were a harmful substance instead of a helpful remedy. For reasons not fully understood, your body creates antibodies called immunoglobulin to attack the medication. In most cases of penicillin allergy, the type of immunoglobulin that causes the most problems is type E (IgE). Risk factors It isn't clear why some people develop allergies while others don't. However, certain people seem to be at greater risk of developing a penicillin allergy than others are. Heredity may play a role. When to seek medical advice Talk to your doctor if you think you're allergic to penicillin or if you experience any signs or symptoms of penicillin allergy. If possible, see your doctor when the allergic reaction is occurring. This will aid in making a diagnosis. Seek emergency medical treatment if you develop any signs or symptoms of anaphylaxis. Screening and diagnosis Your doctor will want to know your history of penicillin allergy signs and symptoms, and may want to conduct a physical examination to identify or exclude other medical problems. He or she may also recommend a skin test. This test, in which your skin is injected with small amounts of penicillin, can determine your sensitivity to the drug. A small amount of penicillin is injected into the skin of your forearm or back. If you're allergic to the particular substance being tested, you develop a red, raised bump or reaction. Only specialized allergy centers are able to perform skin tests for penicillin allergy. Treatment If you experience an allergic reaction to penicillin, you can take an antihistamine such as diphenhydramine (Benadryl, others) to relieve itching and calm a rash. More severe reactions may require treatment with oral or injected corticosteroids. Anaphylaxis is an emergency requiring an immediate epinephrine injection and hospital care to maintain blood pressure and support breathing. Prevention The best way to avoid an allergic reaction to penicillin is to avoid penicillin and similar antibiotics altogether. If you're allergic to penicillin, it doesn't mean you're necessarily allergic to all antibiotics. Your doctor may be able to give you an antibiotic that's distantly related to penicillin without causing any problems. Antibiotics completely unrelated to penicillin also are available. For some infections, it may be absolutely necessary for you to take penicillin. In these cases, and if you previously experienced a reaction to penicillin, an allergy skin test may be important. If the skin test reveals that you're sensitive to penicillin, your doctor may recommend desensitization. During the desensitization process, you receive small but gradually increasing doses of penicillin orally or intravenously. Because desensitization can trigger an allergic reaction, it's attempted only in a controlled hospital setting — and only when penicillin is absolutely necessary. Your desensitization lasts only as long as you continue taking penicillin. If you stop and then need to take penicillin again later, you'll need to go through the desensitization process again. The process of desensitization generally takes one to two days. However, it doesn't work in all cases. It's unknown why this process works for some people and not others. Self-care If you think you've had reactions to penicillin in the past, be sure to tell your doctor and other medical professionals, including your dentist. Let your doctor know about any new reactions you notice when taking your medication. If your doctor determines that you're allergic to penicillin, it's a good idea to wear a medical alert bracelet that describes your allergy, and you might want to carry an alert card in your wallet or purse. These items are available over-the-counter at most drugstores or can be purchased on the Internet. December 22, 2005 |
