Drug Allergies

An allergic reaction occurs when the immune system overreacts to a harmless substance, in this case, the medication. If your immune system detects a drug as a harmful substance, it will develop an antibody specific to that drug. This can happen the first time you take a drug, but sometimes an allergy doesn't develop until there have been repeated exposures. Intolerances or sensitivities to medicine may produce symptoms similar to an allergic reaction, but do not involve the immune system. A drug allergy can be difficult to diagnose, therefore it is important to see an allergy expert if you suspect you have had an allergic reaction to a medication. About 5–10 percent of adverse reactions occur because of a true allergy to the drug.

Adverse reactions to medications are common and may cause a range of symptoms. Mild to moderate allergic reactions can include:

  • Skin rash or hives
  • Itching
  • Wheezing or other breathing problems
  • Swelling
  • Nausea/Vomiting
  • Feeling dizzy or light-headed

A less common, but more serious, allergic reaction is anaphylaxis. This occurs in highly sensitive patients and comes on suddenly, can worsen quickly and can be fatal. Symptoms of anaphylaxis might include not only skin symptoms, but also any of the following:

  • Swelling of the throat, tongue, nose and lips
  • Tightness in the chest, difficulty breathing
  • Dizziness, fainting, or loss of consciousness, which can lead to shock and heart failure

These symptoms require immediate attention at the nearest Emergency Room.

Some medications are more likely to cause allergic reactions than others. The medications that most often cause allergic reactions include:

  • Antibiotics, such as penicillin
  • Aspirin and non-steroidal anti-inflammatory medications, such as ibuprofen
  • Anticonvulsants
  • Monoclonal antibody therapy
  • Chemotherapy

An allergy to penicillin-type drugs is the only one that can be definitively diagnosed through an allergy skin test.

Penicillin Allergy

Penicillin allergy is the most common drug allergy. Nearly 10% of the population report being allergic to penicillin, however, studies have confirmed that over 90% of the people categorized as being allergic to this widely used antibiotic, actually are not. Additionally, being diagnosed as penicillin allergic does not mean you will be for life. In fact, up to 80% will lose their penicillin allergy if they avoid the drug for 10 years. CDC guidelines suggest that before physicians prescribe broad-spectrum antibiotics to a patient thought to be penicillin-allergic, they should be evaluated for true penicillin allergy (IgE-mediated) by an allergist. Unnecessarily avoiding penicillin leads to higher drug costs for patients and healthcare systems, limited and possibly inferior medical treatments, and possible antibiotic resistance.

Penicillin Allergy Diagnosis and Testing

Your allergist will take a detailed medical history including previous drug reactions. They will conduct allergy skin testing which involves pricking the skin with a weakened form of the drug and observing the patient for a reaction. Those who pass the skin tests are seen as at low risk for an immediate acute reaction to the medication. If the skin test is negative, your allergists may also perform an oral drug challenge, giving a single oral dose to confirm the absence of a penicillin allergy. These tests must always be administered by a board-certified allergist in a medical setting.

Those with positive skin tests should avoid penicillin and be treated with a different antibiotic.

Penicillin allergy testing is available at all 17 Atlanta Allergy & Asthma locations.

Useful Resources

American Academy of Allergy Asthma & Immunology

American College of Allergy Asthma & Immunology