Symptoms of a Drug Allergy

Medically Reviewed by Jennifer Robinson, MD on October 28, 2019

You may have some or all of these symptoms:

Most drug allergy symptoms start right after you take the drug, but some may take hours, days or weeks to appear.

When Symptoms Are Severe

A serious, widespread allergic reaction is called anaphylaxis. It may affect skin, airways, and organs. It also happens very quickly after taking a drug, often within minutes or seconds.

Anaphylaxis is an emergency and is life-threatening. Symptoms include:

If you have any of these symptoms, call 911. Use an epinephrine shot if you have one, and take antihistamines to help slow down the reaction. Do not hesitate to use the epinephrine auto-injector. Using it as a precaution will not harm you and could save your life. Even if the reaction goes away, you still need to go to the hospital.

Mild Drug Allergy: What You Should Do

Depending on your situation, your doctor may suggest that you:

  • Stop taking the drug. This may be enough to make symptoms go away. Remember that your doctor needs to know if you stop taking a prescribed medication.
  • Take an antihistamine, like Benadryl (diphenhydramine).
  • Use a prescription medication. Your doctor may want you to take a steroid medicine.
WebMD Medical Reference



American Academy of Allergy, Asthma, and Immunology: "Drug Allergy," "Medications and Drug Allergic Reactions: Tips to Remember."

American College of Allergy, Asthma & Immunology: Drug Reactions and Drug Allergies.

UpToDate: "An approach to the patient with drug allergy," "Drug Allergy: Classification and Clinical Features."

© 2019 WebMD, LLC. All rights reserved.
Click to view privacy policy and trust info