A drug allergy is an allergic reaction to a medication. With an allergic reaction, your immune system, which fights infection and disease, reacts to the drug. This reaction can cause symptoms such as rash, fever, and trouble breathing.
True drug allergy is not common. Less than 5 to 10 percent of negative drug reactions are caused by genuine drug allergy. The rest are side effects of the drug. All the same, it’s important to know if you have a drug allergy and what to do about it.
Why do Drug Allergies Happen?
Your immune system helps protect you from disease. It’s designed to fight foreign invaders such as viruses, bacteria, parasites, and other dangerous substances. With a drug allergy, your immune system mistakes a drug that enters your body for one of these invaders. In response to what it thinks is a threat, your immune system begins to make antibodies. These are special proteins that are programmed to attack the invader. In this case, they attack the drug.
This immune response leads to increased inflammation, which can cause symptoms such as rash, fever, or trouble breathing. The immune response might happen the first time you take the drug, or it may not be until after you’ve taken it many times with no problem.