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:
Trouble breathing or throat feels like its closing
Dizziness or fainting
Hives covering much of the body
Shock or unconsciousness
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. 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.