What is a drug allergy?

A drug allergy occurs when your immune system reacts to a medication in the same way it would react to a virus or bacteria. This differs from side effects, such as nausea or diarrhea, in that side effects may be expected and do not pose any increased safety risk if this same drug is used again in the future. When a person has a true allergy to a medicine, future exposure to the same medicine can have grave consequences.

A drug allergy is a group of symptoms that occur when your body is exposed to a drug to which it has developed a sensitivity. That sensitivity causes your body's immune system to overreact to the drug. A drug allergy may not happen the first time you take a medication, but if you take the drug again, your body's immune system may cause the release of antibodies or certain immune chemicals that can cause symptoms.

Common symptoms of allergies to drugs may include:

•  hives
•  skin and/or eye itching
•  skin rash
•  swelling of the lips, tongue or face
•  wheezing

Less commonly, a life-threatening reaction called anaphylaxis can occur. Symptoms of anaphylaxis may include:

•  abdominal pain or cramping
•  nausea, vomiting and/or diarrhea
•  confusion
•  dizziness, fainting, lightheadedness
•  difficulty breathing
•  rapid pulse
•  heart palpitations

Certain types of medicines are more likely to cause allergic reactions than others. According to the American Academy of Allergy, Asthma and Immunology, those drugs include:

• antibiotics
• chemotherapy medicines
• aspirin and non-steroidal antiinflammatory drugs (NSAIDs) such as ibuprofen
• anticonvulsants
• monoclonal antibodies

Be sure to discuss with your doctor any adverse effect to a drug that you experience. You may need to avoid exposure to the drug in the future, and possibly even wear a bracelet that could tell an emergency physican you are allergic to the drug.