How to Recognize an Allergic Reaction

Allergic reactions happen when the body's immune system overreacts to something that is normally harmless, such as food, pollen, bee stings, or medications. They are extremely common, so it's important to be able to recognize the symptoms they cause. This article will teach you how to recognize an allergic reaction.


  1. 1
    Determine the severity of the allergic reaction. When exposed to an allergen the body may respond with a few mild symptoms or can affect multiple bodily systems. If multiple systems are involved, the condition is called anaphylaxis, which can be life threatening. Each individual has a different tolerance to allergen exposure which can affect how quickly the reaction progresses.
    • It's important to observe to make sure the reaction does not progress to anaphylaxis, and if it does that it is treated with epinephrine.
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    Recognize the symptoms of a mild allergic reaction. [1]
    • Hives (also referred to as "urticaria") - These are red, raised patches of skin that are very itchy. They can be isolated or spread out all over the body.
    • Itchy skin or rashes
    • Red, itchy eyes
    • Nasal congestion, runny nose
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    Recognize the symptoms of a moderate allergic reaction. Know that if left untreated, some moderate allergic reactions may progress to anaphylaxis (see below). You should call the Emergency Services if you are experiencing several of the following symptoms.
    • Swelling of the hands, feet, lips, face, or throat
    • Skin blistering or painful skin
    • Pain or irritation of the moist lining of the mouth, eyes, or vagina
    • Nausea, vomiting, diarrhea, or abdominal pain
    • Wheezing, or chest tightness
    • Hoarseness of the voice or coughing
    • Flushing of the skin
    • Dizziness
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    Recognize the symptoms of a severe allergic reaction called anaphylaxis. Anaphylaxis is full body allergic reaction that is life-threatening because it can cause respiratory collapse and vascular collapse, also known as Anaphylactic Shock. Anaphylaxis should be treated with epinephrine before the symptoms progress. Symptoms include:
    • all symptoms listed above with greater severity. Critical items are:
      • a drop in blood pressure shown as lightheadedness, anxiety or confusion. This can lead to unconsciousness, shock and death.
      • swelling of the throat which feels like a lump in the throat or impedes the ability to talk. This can lead to complete blockage of the airway.
      • These symptoms should be treated with epinephrine using an EpiPen.
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    Recognize severe allergic reactions that involve the skin.
    • Stevens-Johnson Syndrome (SJS). This is a rare but life threatening skin condition in which the outer layer of the skin (called the epidermis) separates from the inner layer of skin (called the dermis). [2] The skin turns red or purple and begins to peel away from the body, and ulcers or blisters may form in the mouth, on the tongue, or genital or anal region. Other symptoms of SJS include:
      • High fever (>102F or 39C)
      • Flu-like symptoms (fever, sore throat, cough)
      • Burning or itching eyes
    • Toxic epidermal necrolysis (TEN) is similar to SJS but more severe because it involves a greater area of the body.
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    Recognize a delayed allergic reaction. Delayed reactions are common, especially several days after starting a new medication. They usually involve an extensive skin rash that may be itchy. This is not a dangerous reaction, and it is not associated with any of the other symptoms of allergic reactions described above.


  • If you notice any of these symptoms, try to pinpoint what the trigger may have been. Think about any recent changes in your diet, any new soaps or detergents, new medications or supplements, or environmental exposures. Knowing the trigger of an allergic reaction is essential for preventing the symptoms from recurring in the future, and it will help your doctor come up with the best treatment plan for you.

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Categories: Allergies and Immunization