Drug Allergy - Causes

Introduction Causes Symptoms Treatments

Any medicine can cause an allergic reaction.

A few of the most common culprits are:

  • Penicillins (such as nafcillin, ampicillin, or amoxicillin). These types of medicines cause the most drug allergies.
  • Sulfa medicines.
  • Barbiturates.
  • Insulin.
  • Vaccines.
  • Anticonvulsants.
  • Medicines for hyperthyroidism.


If you are allergic to one medicine, you may be allergic to others like it. For example, if you are allergic to penicillin, you may also be allergic to similar medicines such as cephalosporins ( cephalexin or cefuroxime, for example).

People with AIDS or lupus may be allergic to many types of medicines. The reactions usually aren't dangerous, but they can make it hard to treat the disease.

Some people-especially those with asthma-have reactions to common pain relievers such as aspirin and ibuprofen. These seem like allergic reactions but they are not, because they do not affect the immune system. But these reactions can be severe in people who have asthma.