Drug Allergy & Allergic Reactions to Medications

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A drug allergy is the abnormal reaction of your immune system to a medication. Any medication — over-the-counter, prescription or herbal — is capable of inducing an allergic reaction. The drugs that cause the most reactions are penicillin and aspirin, affecting up to 10% of the population. Other drugs that trigger allergies include sulfa drugs, anticonvulsants, and chemotherapy drugs.

Allergic reactions to drugs or medications usually do not occur the first time a person takes a specific drug. It could take years to develop a drug allergy after constant exposure. You may also have been exposed to the medication or medication in the same drug class without knowing it. It is important to identify a drug allergy early because the symptoms can be very uncomfortable or even life-threatening. 

Drug Allergy Symptoms

  • Hives or rash
  • Itching
  • Asthma
  • Swelling (of the tongue or lips, for example)
  • Loss of consciousness
  • Anaphylaxis

Many people mistake a drug allergy with a drug side effect. For this reason, it is very important to make sure you tell your NY allergist about all of the medications you have been taking. Common side effects that are not allergic reactions include:

  • Diarrhea
  • Dry mouth
  • Headaches
  • Heartburn
  • Racing heart

It is sometimes difficult to determine if you are experiencing an allergy or a side effect. That’s why we recommend seeking medical attention for any abnormal reactions after taking medications. The allergy physicians at NY Allergy & Sinus Centers will help figure out what is an allergic reaction, as opposed to a side effect of a medication. Allergic reactions can be very dangerous, and we can assist you in identifying the symptoms of allergies.

Drug Allergy Diagnosis

A skin prick test can diagnose a drug allergy; however, it’s not always accurate in detecting all drug allergies. Most often, allergists will use intradermal testing to diagnose your drug allergies. Drugs that are injected can be quickly diagnosed by intradermal testing. During this test, an allergist will introduce the allergen beneath the skin and watch for a reaction. Intradermal testing is more sensitive than skin prick testing, so you may experience uncomfortable reactions. Your doctor will have epinephrine and other allergy medications available to treat any symptoms.

In addition, a drug challenge may be performed. This is only performed in extreme cases when allergy testing cannot confirm a drug allergy. During a drug challenge, a dose of the suspected allergen may be administered in the office under careful observation to confirm the allergy. This is done only as a last option, as some drugs are known to cause severe allergic reactions.

Drug Allergy Treatment

Many drug allergies disappear over time. For those that don’t, desensitization is a treatment option. Desensitization is available for penicillin, aspirin, and some chemotherapeutic drugs. The process involves gradually administering the medication by mouth or as shots to build a tolerance to the drug. This treatment is only necessary for patients with ongoing medical conditions who require certain medications where there aren’t any alternatives.

When possible, avoidance is always the best treatment for allergies. Ask your doctor about alternatives to the drugs you are allergic to. There are usually many options of medications to treat your condition. For example, instead of taking penicillin, you may be prescribed trimethoprim or nitrofurantoin. Be sure to discuss your options with our allergy specialists.

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