First Aid Guide to Allergic Reactions

This content is for informational purposes only and is not intended to provide medical advice or to treat, diagnose, cure or prevent any disease or condition. Always seek the advice of your healthcare provider.

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Understanding Allergic Reactions

An allergic reaction occurs when a person’s immune system produces antibodies to protect them from a seemingly harmful substance (called an allergen). For example, when an allergic person comes in contact with a peanut through taste, touch, or smell, the body reacts to defend against the allergen “invader.” The antibodies of the allergic person cause mast cells to release histamine into the bloodstream to defend against the allergen. It’s the release of these chemicals that causes allergic reactions such as itching, swelling, nausea, and difficulty breathing. The reaction can affect a person’s eyes, nose, throat, lungs, skin, or gastrointestinal tract as the body gears up for attack. Initial exposure to an allergen may cause a mild reaction; however, future exposures to the same allergen will trigger more severe reactions.

Many mild allergic reactions are common, while others can be severe and life-threatening. Allergic reactions occur more often in people who have a family history of allergies. The most severe form is called anaphylaxis or anaphylactic shock.


Common allergens include:

  • Animal dander
  • Bee stings or stings from other insects
  • Foods, especially milk, eggs, nuts, fish, and shellfish
  • Insect bites
  • Medications
  • Plants
  • Pollens
  • Signs of an Allergic Reaction

    Common symptoms of a ​mild​ allergic reaction include:

  • Hives (especially over the neck and face)
  • Itching
  • Nasal congestion
  • Rashes
  • Watery, red eyes
  • Symptoms of a ​moderate​ or ​severe​ reaction include:

  • Abdominal pain
  • Difficulty breathing and/or swallowing
  • Anxiety
  • Chest discomfort or tightness
  • Cough or throat swelling/closing
  • Diarrhea
  • Dizziness or light-headedness
  • Flushing or redness of the face
  • Nausea or vomiting
  • Swelling of the face, eyes, or tongue
  • Unconsciousness
  • First Aid Treatment

    For a ​mild​ to ​moderate​ reaction:

    1. Stay calm and reassure the person having the reaction. Anxiety can worsen symptoms.
    2. Try to identify the allergen and have the person avoid further contact with it.
    3. If the person develops a rash or hives, apply cool compresses and an over-the-counter hydrocortisone cream.
    4. Watch the person for symptoms that worsen.
    5. Contact a doctor. For a mild reaction, a health care provider may recommend
    over-the-counter medications, such as antihistamines.

    For a​ severe ​allergic reaction (anaphylaxis):

    1. Call 911.
    2. Check the person’s airway, breathing, and circulation. A swollen throat will cause a very hoarse voice and difficulty breathing. If necessary, begin rescue breathing and CPR.
    3. Stay calm and reassure the person.
    4. If the person has emergency allergy medication on hand, such as an epinephrine injection*, help the person take or inject the medication. ​Avoid oral medication if the person is having difficulty breathing. Antihistamines, such as Benadryl, will not relieve severe symptoms of anaphylaxis.
    5. In order to prevent shock, have the person lie flat, raise the person’s feet about 12 inches, and cover him or her with a coat or blanket.

    *After receiving epinephrine, the affected person should go immediately to a hospital emergency department, where additional treatment can be given. It is common for allergic reaction symptoms to resurface after a couple of hours of receiving epinephrine.

    Preventing Allergic Reactions

    There are no cures for allergies; however, there are ways to manage them to avoid a reaction:

  • Visit an Allergist. They may recommend ​immunotherapy ​(allergy shots) for allergens such as dust, mold, pollens, animals, and insect stings.
  • Take prescription or over-the-counter medicines, including antihistamines, eye drops, and nasal sprays​.
  • Avoid triggers such as foods and medications that have caused an allergic reaction in the past. Reduce your exposure to environmental allergens.
  • For food allergies, ask detailed questions about ingredients when you are eating out. Notify your waiter or waitress of your allergy. Carefully check ingredient labels. Know the technical names for ingredients you should avoid.
  • Persons who have had serious allergic reactions should carry emergency medications (such as injectable epinephrine) according to your health care provider’s instructions.
  • Make sure all caregivers of a child with a severe allergy are aware of the signs of a reaction and understand the emergency protocol. Have your child wear a medical bracelet stating their allergy.
  • By taking preventive measures and treatments, people with allergies can enjoy happy, healthy lives.

    Tips to Avoid Environmental Allergens:

    • Remove carpets or rugs from your house or bedroom (hard floor surfaces don’t collect dust as much as carpets do).
    • Clean regularly.
    • Use special hypoallergenic covers to seal pillows and mattresses.
    • Keep the windows closed when the pollen season is at its peak, and change your clothing and shower after you’ve been outdoors.
    • Stay away from damp areas, such as basements, and keep​ ​bathrooms and other mold-prone areas clean and dry.
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