Anaphylaxis is a severe allergic reaction. It can lead to a potentially fatal condition known as anaphylactic shock.

Common substances that the body reacts to include food, insect bites, venom, and medication. These are called allergens.

Food allergy is the main cause of anaphylaxis outside of the hospital, according to Food Allergy Research and Education (FARE).

Anaphylactic reaction to food is responsible for one emergency department visit every 3 minutes in the United States (U.S.), mostly in teenagers and young adults.

The most common triggers are medications, foods, and insect stings.

Fast facts about anaphylaxis

  • Anaphylaxis is a severe allergic reaction.
  • It can cause breathing problems, plummeting blood pressure, shock, and potentially death.
  • Anaphylactic reactions to allergens in food cause one hospital visit every 3 minutes in the U.S.
  • An adrenalin shot, such as from an EpiPen, can help to stop the progression of symptoms.
  • Avoiding known allergens can reduce the risk of anaphylaxis. However, if an allergen has never caused reaction before, there is no way to prepare for its anaphylactic reaction.

    Woman experiencing anaphylactic shock coughing into hand holding chest having difficulty breathingShare on Pinterest
    Symptoms of anaphylaxis can include difficulty breathing, coughing, and a feeling that something is stuck in the throat.

    Many people react to a substance, or allergen, with watery eyes, a runny nose, and maybe a rash. However, a severe allergic reaction can lead to a serious condition known as anaphylaxis.

    Anaphylaxis happens when the body reacts badly to a substance, or allergen, as if it were a threat to health, like bacteria or a virus.

    The body produces large amounts of histamine, and this triggers an inflammatory response.

    This response can lead to a dilation of the blood vessels, a sudden drop in blood pressure, loss of consciousness, and shock. As the airways narrow, breathing becomes difficult. The blood vessels may leak, resulting in edema, or swelling, in surrounding tissue.

    The reaction may happen at once, within hours, or, very occasionally, some days after coming into contact with the allergen.

    It is important to know the signs and symptoms of anaphylaxis, because urgent action may be needed.

    They include:

    • difficulty breathing, wheezing, shortness of breath, tightness in the throat and chest pain
    • trouble swallowing
    • a cough and a hoarse voice
    • itchy mouth or throat and nasal congestion
    • feeling that something is stuck to the tongue, or in the throat
    • a full and heavy feeling in the tongue
    • swelling and itchiness on the skin, with hives, warmth, redness, and a rash
    • stomach pain and cramps, with nausea, vomiting, and diarrhea
    • anxiety and a feeling of impending doom
    • swelling of the feet, hands, lips, eyes, and sometimes the genitals
    • low blood pressure and poor circulation leading to pale blue skin, a low pulse, dizziness, or faintness
    • shock
    • loss of consciousness

    The person may also have itchy, red, watery eyes, a headache, and cramping of the uterus. They may have a metallic taste in the mouth.

    Severe breathing difficulties, a serious drop in blood pressure, or both can lead to shock, and this can be fatal.

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    If you see someone experiencing anaphylaxis, make sure they are still breathing while emergency services are on their way to help.

    If a person starts to show severe allergic symptoms, urgent medical attention is needed.

    First aid for anaphylaxis includes:

    • removing the allergen, if possible, and calling for emergency assistance
    • finding out if the patient has a history of allergy
    • helping them administer any medication they may have
    • reassure the patient so that they feel comfortable

    If the patient knows they are allergic, they may have medication in the form of an adrenalin injection kit, such as an EpiPen, that they can use.

    The injector will provide a dose of epinephrine, a form of adrenalin.


    While waiting for help, the person who is with the patient should make sure they can breathe.

    To make breathing easier, the person should stay sitting up, but if there is a drop in blood pressure, they should be laid down flat on the ground with their legs raised.

    If they faint, someone should make sure they can breathe. They can be placed in the recovery position.

    Whoever stays with the patient should monitor their condition.

    When a health care provider arrives, be ready to tell them, if possible:

    • what caused the reaction
    • whether the person experiencing anaphylaxis has self-medicated

    If possible, keep a sample of the item that caused the reaction, and have it accompany the patient to the hospital.

    Should breathing stop completely, cardiopulmonary resuscitation (CPR) should be done and continued until the rescue team arrives.

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    An EpiPen is a common treatment for severe allergic reactions.

    Emergency help for a patient with severe anaphylaxis will be an epinephrine, or adrenalin, injection.

    Adrenalin, also known as epinephrine, works in several ways.

    • It causes the blood vessels to constrict, and this decreases swelling and helps increase blood pressure.
    • It helps relax the muscles around the lung.
    • It prevents the release of additional allergic chemicals.

    This helps to stop the reaction from progressing further.

    Most patients respond well to this treatment, and symptoms normally start to subside at this point. If there is no improvement, the patient will receive another dose after 10 minutes.

    Sometimes, symptoms subside after taking adrenalin but then come back. The patient may be kept under observation in the hospital for 24 hours.

    For a less severe reaction, the doctor may give corticosteroid or antihistamine injections.

    Anaphylaxis is a life-threatening emergency. People who are most susceptible to it are those with allergies.

    However, it is not always predictable. Some people react to a substance that has not affected them previously.

    After having an allergic reaction, the person should remember what caused it, and try to avoid it in future.

    As it is not always possible to avoid an allergen, they may need to carry an injector and wear a bracelet to let other people know that they have an allergy People should let their friends, employers, or school staff know about any allergies that could cause a severe reaction.

    Anaphylaxis is a potentially life-threatening emergency that needs immediate assistance. Everyone should know the signs and symptoms, and how to react.