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Drug Allergies

Many drugs can cause adverse side effects and certain medicines can trigger allergies. In an allergic reaction, the immune system mistakenly responds to a drug by creating an immune response against it. The immune system recognizes the drug as a foreign substance and the body produces certain chemicals, such as large amounts of histamine in an attempt to expel the drug from the body.

What Are the Symptoms of a Drug Allergy?

Symptoms of a drug allergy can range from mild to life-threatening. Even in people who aren't allergic, many drugs can cause irritation, such as an upset stomach. But during an allergic reaction, the release of histamine can cause symptoms like hives, skin rash, itchy skin or eyes, congestion, and swelling in the mouth and throat.

A more severe reaction may include difficulty breathing, blueness of the skin, dizziness, fainting, anxiety, confusion, rapid pulse, nausea, diarrhea, and abdominal problems.

What Are Some Common Drug Allergies?

The most common drug allergy is penicillin. Other antibiotics similar to penicillin can also trigger allergic reactions.

Other drugs commonly found to cause reactions include sulfa drugs, barbiturates, anticonvulsants, insulin, and iodine (found in many X-ray contrast dyes).

How Are Drug Allergies Diagnosed?

A doctor diagnoses a drug allergy by carefully reviewing your medical history and symptoms. If your doctor suspects that you are allergic to an antibiotic such as penicillin, he or she may do a skin test to confirm it. However, skin testing does not work for all drugs and, in some cases, it could be dangerous. If you have had a severe, life-threatening reaction to a particular drug, your doctor will simply rule out that drug as a treatment option. Conducting an allergy test to determine if the initial reaction was a "true" allergic response isn't worth the risk.

 

What Is the Treatment for Drug Allergies?

The primary goal when treating drug allergies is symptom relief. Allergy symptoms such as rash, hives, and itching can often be controlled with antihistamines and, occasionally, corticosteroids.

For coughing and lung congestion, drugs called bronchodilators may be prescribed to widen the airways. For more serious anaphylactic symptoms -- life-threatening reactions including difficulty breathing or loss of consciousness -- epinephrine may be given.

Occasionally, desensitization is used for penicillin allergy. This technique decreases the body's sensitivity to particular allergy-causing agents. Tiny amounts of penicillin are injected periodically in increasingly larger amounts until your immune system learns to tolerate the drug.

If you are severely allergic to certain antibiotics, there are alternative antibiotics your doctor can prescribe.

How Can I Be Prepared if I Have a Drug Allergy?

If you have a drug allergy, always inform your health care provider before undergoing any type of treatment, including dental care. It is also a good idea to wear a MedicAlert bracelet or pendant, or carry a card that identifies your drug allergy. In cases of emergency, it could save your life.

WebMD Medical Reference

Reviewed by Jonathan L Gelfand, MD on May 14, 2012
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