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Allergic Reaction (cont.)

What Causes an Allergic Reaction?

Almost anything can trigger an allergic reaction.

  • The body's immune system involves the white blood cells, which produce antibodies.
    • When the body is exposed to an antigen (a foreign body such as pollen that can trigger an immune response), a complex set of reactions begins.
    • The white blood cells produce an antibody specific to that antigen. This is called "sensitization."
    • The job of the antibodies is to help white blood cells detect and destroy substances that cause disease and sickness. In allergic reactions, the antibody belongs to the class of immunoglobulins known as immunoglobulin E or IgE.
  • This antibody type promotes production and release of chemicals and hormones called "mediators."
    • Mediators have effects on local tissue and organs in addition to activating more white blood cell defenders. It is these effects that cause the symptoms of the reaction.
    • Histamine is one of the better-known allergy mediators produced by the body.
    • If the release of the mediators is sudden or extensive, the allergic reaction may also be sudden and severe, and anaphylaxis may occur.
  • Allergic reactions are unique for each person. Reaction time to allergens can vary widely. Some people will have an allergic reaction immediately; for others, it may take hours to days to develop.
  • Most people are aware of their particular allergy triggers and reactions.
    • There are more than 160 allergenic foods. Certain foods are common allergens, including peanuts, strawberries, shellfish, shrimp, dairy, and wheat.
    • Babies can also have food allergies. Common foods that can cause allergic reactions in babies include milk, eggs, nuts, and soy. People should talk to their child's pediatrician if they are concerned about food allergies in their baby.
    • Food intolerance is not the same as food allergies. Allergies are an immune system response, while food intolerance is a digestive system response in which a person is unable to properly digest or break down a particular food.
    • People can be allergic to wheat but not gluten. According to the American College of Allergy, Asthma & Immunology, there is no such thing as a gluten allergy; but one can have a sensitivity to this protein that results in gastrointestinal symptoms.
    • Certain fruits or vegetables may cause an itchy mouth or scratchy throat after eating in people who have oral allergy syndrome.
  • Seasonal allergic rhinitis (also called hay fever) is an allergy that occurs in the spring, summer, or early fall caused by allergies to pollens from trees, grasses or weeds, or to mold spores.
  • Vaccines and medications (antibiotics such as penicillin and amoxicillin, aspirin, ibuprofen, iodine), general anesthesia and local anesthetics, latex rubber (such as in gloves or condoms), dust, mold or other fungi, animal dander from pets and other animals, and poison ivy are well-known allergens. Other known allergens can include detergents, hair dyes, cosmetics, and the ink in tattoos.
  • Bee stings, fire ant stings, penicillin, and peanuts are known for causing dramatic reactions that can be serious and involve the whole body.
  • Minor injuries, hot or cold temperatures, exercise, stress, or emotions may trigger allergic reactions.
  • Sun exposure may cause allergic reactions in some people, often referred to as "sun poisoning."
  • Often, the specific allergen cannot be identified unless someone has had a similar reaction in the past.
  • Allergies, and the tendency to have allergic reactions, is hereditary -- that is, it runs in some families.
  • Many people who have one trigger tend to have other triggers, as well.
  • Risk factors for allergic reactions include certain medical conditions that can make a person more likely to have allergic reactions:
Last Reviewed 9/11/2017

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