Allergy flat vertical banner set with respiratory symptoms food allergens elements isolated vector illustration
An allergy is a heightened immune response to something in the environment.

People can be allergic to a variety of substances. According to the Asthma and Allergy Foundation of America, “Allergies are grouped by the kind of trigger, time of year or where symptoms appear on the body: indoor and outdoor allergies (also called “hay fever,” “seasonal,” “perennial” or “nasal” allergies), food allergies, latex allergies, insect allergies, skin allergies and eye allergies.”

Percentage of Children under 18 with Reported Food, Skin, or Hay Fever/Respiratory Allergies

National Health Interview Survey, United States, 1998–2009
An allergy develops in several stages:

  1. A potential environmental trigger, pollen for example, is recognized as a foreign material. This first exposure can happen through inhalation, ingestion, touch, or injection.
  2. The person becomes sensitized but no reaction occurs. Sensitization occurs if a person has a predisposition to pollen allergies. The body generates IgE antibodies which will start the allergy response symptoms whenever the body is exposed to pollen in the future.
  3. The next step occurs the second time you are exposed to pollen. With the second exposure, the IgE antibodies recognize the pollen as dangerous and start the allergy response cascade. This is the first time the person experiences any symptoms –sneezing, wheezing, itchy eyes, etc.

The last step can happen in two phases, the early and late phases. The late phase is prolonged and can have more intense or severe symptoms.

Symptoms of an allergic reaction can affect different areas of the body:

  • Skin: itching, redness and hives
  • Airway: sneezing, coughing, and wheezing
  • Gastrointestinal tract: cramping and diarrhea


A serious allergic reaction is called anaphylaxis. It is characterized by more intense symptoms along with abnormal and difficult breathing, chest tightness, anxiety, swelling of the face, eyes, or tongue, and racing heart. These symptoms can lead to loss of consciousness and are life threatening.

  • The most common causes of anaphylaxis
  • Medications: antibiotics, dyes, vaccine ingredients such as gelatin and egg protein
  • Foods: peanuts, tree nuts, cow’s milk, eggs, and seafood
  • Stinging insects
  • Latex
  • Blood products

Long-term Effects of Allergies

Many symptoms of an allergic reaction are short lived, but there are long term consequences of repeat reactions. The inflammatory effects of allergic reactions can change the structure of the systems it affects (such as skin, airway, or gastrointestinal tract). For example, structural changes of the airways can lead to asthma or chronic ear and sinus infections. Changes in the gastrointestinal tract can cause malabsorption, and changes to the skin can lead to eczema 2.

Many children who exhibit skin allergies through eczema also develop food allergies, and vice versa.

allergy response

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