Drug Allergy - Introduction

Introduction Causes Symptoms Treatments

A drug allergy happens when you have a harmful reaction to a medicine you use. Your body’s immune system fights back by setting off an allergic reaction. Most drug allergies are mild, and the symptoms go away within a few days after you stop using the medicine. But some drug allergies can be very serious.

Some drug allergies go away with time. But after you have an allergic reaction to a drug, you will probably always be allergic to that drug. You can also be allergic to other drugs that are like it.

A drug allergy is one type of harmful, or adverse, drug reaction. Symptoms and treatments of different kinds of adverse reactions vary. So your doctor will want to find out if you have a true drug allergy or if you have another type of bad reaction that isn't as serious.


What to think about


  • People with AIDS or lupus may have more drug allergies than other people. While the reactions are usually not life-threatening, they make treating the disease more difficult.
  • If you are allergic to one medicine, you may be allergic to other closely related medicines. For example, if you are allergic to penicillin, you may also be allergic to similar antibiotics such as cephalosporins ( cephalexin or cefuroxime, for example).