Anaphylaxis is a severe allergic reaction that can be life-threatening. This reaction can happen in a few minutes, or a few hours after exposure to what you are allergic to (allergen).

The symptoms of an anaphylactic reaction may seem like other allergic reactions at first. Don't let the early mild symptoms, such as a rash, hives, and itching, mislead you. Your reaction can get worse very quickly and become life-threatening within minutes.

Severe symptoms of anaphylaxis include:

  • Trouble swallowing, feeling like your throat is closing

  • Trouble breathing, coughing, or wheezing

  • Chest pain or tightness

  • Cool, moist, or pale (blue in color) skin

  • Hoarse voice or trouble speaking

  • Upset stomach (nausea), vomiting, diarrhea, stomach cramps, or pain

  • Feeling faint or lightheaded

  • Fast heart rate

  • Low blood pressure

  • Feeling dizzy or confused

  • Becoming very drowsy, poorly responsive, or having trouble waking up

  • Seizure

  • Swelling of the eyes, mouth, face, or tongue

  • Anxiety

  • Hives, rash, or itchy skin

Sometimes the cause of the reaction may be obvious if you have a known allergy. If you know the cause of your reaction, prevent exposure to the allergen in the future. If you don't know the cause, follow up with your healthcare provider for special testing to find out what you're allergic to. To help find out an unknown allergen, remember:

  • When the reaction started

  • What you were doing at the time or just before that

  • Any new products or contacts

Almost anything can cause a reaction. You may not even be aware that you had contact with an allergen. Allergies to dust, pollens, and animals rarely cause anaphylaxis. Here are some common causes of anaphylaxis:

  • Foods such as shellfish, peanuts, tree nuts, milk products, wheat, eggs; also, colorings, flavorings, additives

  • Insect bites or stings such as bees, wasps, hornets, or fire ants

  • Medicines such as penicillin, sulfa, aspirin, ibuprofen; any medicine can cause a reaction

  • Latex such as in gloves, clothes, toys, balloons, or some tapes; some people allergic to latex may also have problems with foods like bananas, avocados, kiwi, papaya, or chestnuts

If you're exposed to the same substance again, you may have the same or a more severe reaction.

Home care

Once you're stabilized in the emergency room and it's safe for you to go home, watch for any worsening symptoms. Call 911 if symptoms get worse. You may need to be treated again.


Injectable epinephrine

One of the key tools in treating anaphylaxis is early use of epinephrine. If you had a severe allergic or anaphylactic reaction, the healthcare provider may prescribe a self-injectable epinephrine kit with 2 epinephrine injectors. If this was prescribed, always carry both epinephrine injectors. It can be lifesaving. Epinephrine can help stop the progression of an allergic reaction. Its effects are brief. So after you use the medicine, it's still very important to call 911 right away and get to an emergency room.

When to use injectable epinephrine

Use the epinephrine if you have any of these symptoms, or as advised by your healthcare provider:

  • Swelling in your mouth or throat 

  • Trouble speaking or swallowing

  • Trouble breathing

  • Feeling faint, low blood pressure, or becoming drowsy or poorly responsive

  • Rash that gets worse

Ask your healthcare provider or pharmacist to teach you how to use your injectable epinephrine.

  • Injectors are designed to be injected into the outside of the upper thigh.

  • Be careful not to stick your fingers or hand with the needle.

  • You can inject it through pants, but make sure not to inject it into the seam of the pants.

  • Don't pull it out right away. Try to hold the needle in place for 10 seconds.

  • Massage the spot for a few seconds or as advised by your healthcare provider.

  • If you're injecting it in someone else or a child, try to hold them or their leg still. If they jerk or yank their legs away as you're doing it, it can cause a cut on their leg.

You may feel shaky, jittery, nervous, and anxious after the injection. Although it's hard, try to relax. This is a side effect of the epinephrine. It should stop after a few minutes. 


  • Call 911 or go to the emergency room immediately after using the epinephrine. Its effect will wear off, and you may have a second reaction. This could even happen hours later.

  • If your symptoms start to return 5 to 15 minutes after using your epinephrine injector and help hasn't arrived yet, use the second injector.

  • Never knowingly eat, use, or expose yourself to the substance that caused the anaphylactic reaction. Nothing is foolproof, including the injectable epinephrine.

Other medicines

The healthcare provider may prescribe medicine to ease swelling, itching, and pain. Follow the provider's instructions when using this medicine. 

  • Oral diphenhydramine is an antihistamine available at drug and grocery stores. Unless a prescription antihistamine was given, diphenhydramine may be used to reduce itching if large areas of the skin are involved. It may make you sleepy, so be careful using it in the daytime or when going to school, working, or driving. Talk with your provider before using antihistamines if you have glaucoma, thyroid disease, high blood pressure, heart disease, breathing problems, or if you have trouble peeing due to an enlarged prostate.

  • Don't use diphenhydramine cream on your skin because in some people it can cause a further reaction.

  • You may use over-the-counter acetaminophen or ibuprofen to control pain, unless another pain medicine was prescribed. Ask your healthcare provider what medicines are safe for you, especially if you have heart, kidney, or liver disease, are taking blood thinners, are at risk for gastrointestinal ulcers or bleeding, or have high blood pressure.

  • If you were prescribed any medicines to prevent symptoms from returning, be sure to take them exactly as directed.

General care

  • Rest at home for the next 24 hours.

  • Don't use tobacco or drink alcohol. These may make your symptoms worse.

  • If you know what caused your reaction today, stay away from that in the future. Let your family members, friends, and personal healthcare provider know about your allergic reaction.

  • If your allergy was to food, learn how to read food labels so you can check for that ingredient. If a product doesn't have a label, it's best to stay away from it.

  • Consider carrying an ID card or getting a medical alert bracelet to inform medical staff of your condition in case you can't tell them.

  • Tell all your healthcare providers that you had an anaphylactic reaction. Make sure the information is added to your medical records.

Follow-up care

Follow up with your healthcare provider or as advised if you aren't improving over the next 1 to 2 days.

Call 911

Call 911 if any of these occur:

  • Trouble breathing or swallowing, wheezing

  • Hoarse voice or trouble speaking

  • Chest pain or tightness

  • Confusion

  • Very drowsy or trouble awakening

  • Fainting or loss of consciousness

  • Fast heart rate

  • Low blood pressure

  • Vomiting blood, or large amounts of blood in stool

  • Seizure

  • Swelling in the eyes, mouth, face, or tongue

  • Dizziness or weakness

  • Cool, moist, or pale (blue in color) skin

  • Nausea, vomiting, diarrhea, stomach cramps, or belly (abdominal) pain

When to get medical advice

Call your healthcare provider right away if any of these occur:

  • Your symptoms get worse

  • New symptoms

  • Symptoms don't go away or come back

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