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Drug Allergy: Care Instructions


A drug allergy occurs when your immune system overreacts to something in a medicine. This causes an allergic reaction. You may have skin problems, such as hives, a rash, or itching. Your lips, mouth, and throat may swell. You may have trouble breathing. And you may have belly pain, nausea, vomiting, or diarrhea. A reaction can range from mild to life-threatening.

After you have an allergic reaction to a medicine, you may always be allergic to that medicine and to others like it.

Drug allergies are different than side effects and drug interactions. Side effects are reactions to medicines that aren't caused by the immune system. Drug interactions occur when two or more medicines that you take don't work well together in your body. Some people may confuse these with drug allergies. Talk to your doctor if you think you have a problem with your medicine.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

How can you care for yourself at home?

  • Your doctor may prescribe a shot of epinephrine to carry with you in case you have a severe reaction. Learn how to give yourself the shot, and keep it with you at all times. Make sure it has not expired.
  • Go to the emergency room every time you have a severe reaction. Go even if you have used your shot of epinephrine and are feeling better. Symptoms can come back after a shot.
  • If you were given a medicine for your allergic reaction, take it exactly as directed. Call your doctor or nurse advice line if you think you are having a problem with your medicine.
  • Avoid medicines like the one that caused your allergy. Ask your doctor or pharmacist if you think you may be taking a similar medicine.
  • If you have a mild skin rash or itching from your allergy:
    • Wear light clothing that does not irritate your skin.
    • Use calamine lotion. Or take a non-drowsy antihistamine, such as loratadine (Claritin). Be safe with medicines. Read and follow the instructions on the label.
    • Take a cool shower or bath.
    • Do not use strong soaps, detergents, and other chemicals. They can make itching worse.
  • Wear medical alert jewellery that lists your allergies.
  • Be sure that anyone treating you for any health problem knows that you are allergic to this medicine.

When should you call for help?

Give an epinephrine shot if:

  • You think you are having a severe allergic reaction.

After giving an epinephrine shot, call 911, even if you feel better.

Call 911 if:

  • You have symptoms of a severe allergic reaction. These may include:
    • Sudden raised, red areas (hives) all over your body.
    • Swelling of the throat, mouth, lips, or tongue.
    • Trouble breathing.
    • Passing out (losing consciousness). Or you may feel very light-headed or suddenly feel weak, confused, or restless.
    • Severe belly pain, nausea, vomiting, or diarrhea.
  • You have been given an epinephrine shot, even if you feel better.

Call your doctor or nurse advice line now or seek immediate medical care if:

  • You have symptoms of an allergic reaction, such as:
    • A rash or hives (raised, red areas on the skin).
    • Itching.
    • Swelling.
    • Mild belly pain or nausea.

Watch closely for changes in your health, and be sure to contact your doctor or nurse advice line if:

  • You do not get better as expected.

Where can you learn more?

Go to

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.