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Allergen: A substance that triggers an allergic reaction.

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Allergic Rhinitis: An allergy affecting the mucus membrane of the nose. Seasonal allergic rhinitis is often called "hay fever."

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Allergist: A doctor that diagnoses, treats, and manages allergy-related conditions.

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Ana-Kit: A device used to inject epinephrine during an anaphylaxis attack.

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Anaphylaxis: A life-threatening allergic reaction that involves the entire body. Anaphylaxis may result in shock or death, and thus requires immediate medical attention

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Animal dander: The small scales or pieces of skin, often containing proteins secreted by oil glands, which are shed by an animal. These proteins are the major causes of allergies to pets.

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Antibiotics: A class of medications used to treat bacterial infections. Certain antibiotics, such as penicillin, may cause an allergic reaction in some people.

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Antibody: A protein in the immune system that recognizes and attacks foreign substances in the body.

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Anticonvulsant: A medication used to prevent or treat seizures. Certain anticonvulsants may cause an allergic reaction in some people.

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Antihistamines: A class of medications used to block the action of histamines in the body and prevent the symptoms of an allergic reaction.

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Asthma: An inflammatory disorder of the airways, causing periodic attacks of wheezing, coughing, chest tightness, and shortness of breath.

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Atopic dermatitis: A chronic skin rash, also known as "eczema," that often appears in the first few years of life.

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Basophil: An immune system cell that attaches to antibodies and circulates through out the blood.

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Beta-blockers: A class of blood pressure medications that ease the heart's pumping action and widen the blood vessels. Beta-blockers counteract the effects of epinephrine used for emergency treatment of anaphylactic shock and should not be used during immunotherapy.

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Bronchial tubes: The lower sections of the airway that lead into the lungs.

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Challenge test: A test used to confirm an allergy to specific substance. A doctor will administer small but increasing amounts of a suspected allergen until an allergic response is noticed. Due to the risk of anaphylaxis, this should only be performed under a controlled setting.

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Conjunctivitis: Inflammation of the conjunctiva, or the mucous membrane surrounding the eye. Also known as pinkeye.

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Contact dermatitis: An allergic reaction resulting from skin contact to an allergen.

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Corticosteroid: An anti-inflammatory medication used to treat the itching and swelling associated with some allergic reactions.

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Cromolym sodium: An anti-inflammatory nasal spray used to treat and sometimes prevent allergic rhinitis.

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Decongestants: A class of medications used for nasal congestion. Decongestants are available in oral doses, nasal sprays, or eye drops (for conjunctivitis).

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Dust mites: A microscopic organism that lives in dust.

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Eczema: See Atopic dermatitis.

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Eosinophil: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Epinepherine: A medication used for immediate treatment of anaphylaxis by raising blood pressure and heart rate back to normal levels. Epinepherine is also known as adrenaline.

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EpiPen: A device used to inject epinephrine during an anaphylaxis attack.

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Heparin: A chemical released by basophils and mast cells that causes nearby tissues to become swollen and inflamed.

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Histamine: A chemical released by basophils and mast cells that causes nearby tissues to become swollen and inflamed.

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Hives: See urticaria.

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Hypertension: High blood pressure. When blood pushes against artery walls harder than normal.

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Immunoglobulin E: A type of antibody responsible for most allergic reactions.

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Immunotherapy: A series of shots that help build up the immune system's tolerance to an allergen.

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Insulin: A hormone that regulates blood sugar levels. Diabetics who take insulin derived from animals may have allergic reactions.

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Intradermal test: A test where an allergen is injected just underneath the skin. Intradermal tests are generally used when results from a skin prick test are unclear.

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Late Phase: The period 4 - 24 hours after exposure to an allergen where tissue damage may occur.

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Leukotrienes: Inflammatory substances that are released by mast cells during an allergic response or asthma attack.

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Lymphocyte: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Mast cell: An immune system cell which attaches to antibodies and is located in the tissue that lines the nose, bronchial tubes, gastrointestinal tract, and the skin

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Neocromil sodium: An inhaled medication used to treat inflammation involved with asthma.

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Neutrophil: A specific type of immune cell that can cause tissue damage in the late phase of an allergic reaction.

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Otitis media: A middle ear infection. Otitis media with effusion occurs when fluid builds up within the ear.

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Radioallergosorbant Test (RAST): A blood test that measures the amount of IgE antibody produced when the sample is mixed with a specific allergen.

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Rhinitis: An inflammation of the nasal passageways, particularly with discharge.

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Sinusitis: An inflammation or infection of one or more sinuses. The sinuses are hollow air spaces located around the nose and eyes.

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Skin prick test: A test where a needle is used to scratch the skin with a small amount of allergen. A response can usually be seen within 15 - 20 minutes.

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Urticaria: Raised areas of the skin that are often red, warm, and itchy. Urticaria is also known as hives.

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Urushiol: An oil found on poison ivy, oak, and sumac.

An immediate allergic reaction involves two actions of your immune system:

Your immune system produces immunoglobulin E (IgE), a protein called a food-specific antibody. IgE circulates through the blood and works against a specific food. A person's ability to form IgE against something as benign as food is an inherited predisposition. Generally, such people come from families in which allergies are common -- not necessarily food allergies, but perhaps hay fever, asthma, or hives. Someone with two allergic parents is more likely to develop food allergies than someone with one allergic parent.

The food-specific IgE then attaches to mast cells. These cells are in all body tissue, but are more often found near sites of allergic reactions, such as the nose, throat, lungs, skin, and gastrointestinal (GI) tract.

If your immune system tends to form IgE to certain foods, you must be exposed to the food before you can have an allergic reaction. When you digest this food, it triggers your body to produce a food-specific IgE in large amounts. The food-specific IgE attaches to the surfaces of mast cells. The next time you eat that food, it interacts with food-specific IgE on the surface of the mast cells and triggers the cells to release chemicals such as histamine.

Depending upon the tissue in which they are released, these chemicals will cause you to have various symptoms of food allergy. Food allergens are proteins within the food that enter your bloodstream after the food is digested. From there, they go to target organs, such as your skin or nose, and cause allergic reactions. An allergic reaction to food can take place within a few minutes to an hour. The process of eating and digesting food affects the timing and the location of a reaction.

  • If you are allergic to a particular food, you may first feel itching in your mouth as you start to eat the food.
  • After the food is digested in your stomach, you may have GI symptoms such as vomiting, diarrhea, or pain.
  • When the food allergens enter and travel through your bloodstream, they may cause your blood pressure to drop.
  • As the allergens reach your skin, they can cause hives or eczema.
  • When the allergens reach your lungs, they may cause asthma.

Read more about food allergies:

Created by the National Institute of Allergy and Infectious Diseases. Modified and updated by A.D.A.M., Inc. Illustration copyright A.D.A.M., Inc.

 

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Review Date: 4/4/2007

Reviewed By: Alan Greene, M.D., F.A.A.P., Department of Pediatrics, Packard Children's Hospital, Stanford University School of Medicine; Chief Medical Officer, A.D.A.M., Inc.


The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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