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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.

Allergy testing can let you know for certain which allergens are affecting you. Testing may reveal allergens that you didn't even realize were causing you problems. Furthermore, testing is necessary if you wish to start immunotherapy (allergy shots).

The allergist will ask questions about your medical history to determine whether allergies run in your family. The allergist may ask detailed questions about your symptoms, what you did to treat those symptoms, and whether it worked. Once non-allergic conditions are ruled out and allergy is suspected, your allergist will perform a diagnostic allergy test.

Skin prick or scratch test

When most people go to the allergist for the first time, they want to know right away -- "What am I allergic to?" Fortunately, skin testing can usually be done on your first visit, and you may get immediate answers to your questions. However, some medications may affect the accuracy of the test, such as antihistamines and antidepressants. If you are taking any prescription medications, ask your primary care physician and allergist how to prepare for the allergy tests.

The skin prick or scratch test is the most common, reliable test for most allergies. The procedure is fairly painless. A small needle or plastic device is used to lightly prick or scratch your back or forearm with a tiny amount of allergen. After 15 - 20 minutes, your allergist will be able to interpret the results by examining each spot where allergens were scratched or pricked into your skin. The spots where you are allergic will become red and swollen, and the others will remain normal.

Intradermal test

The intradermal test is done when the skin prick or scratch test results are unclear. It is similar to the prick or scratch test, but involves injecting a small amount of allergen under the skin using a needle.

Reactions to skin testing should clear up quickly. Because skin testing involves the injection of allergens under the skin, there is a small risk of anaphylaxis. For this reason, allergy skin testing should only be performed in a medical setting, with access to emergency treatment.

Blood test

The blood test or RAST (radioallergosorbent) test measures the levels of the allergy antibody IgE that is produced when your blood is mixed with a series of allergens in a laboratory. If you are allergic to a substance, the IgE levels may increase in the blood sample. The blood test may be used if you have existing skin problems like eczema, if you're on medications that are long-acting or you cannot stop taking, if you have a history of anaphylaxis, or if you prefer not to have a skin test. Some drawbacks of the blood test are the cost and the time required to wait for the results. Also, other conditions are associated with elevated IgE levels (such as HIV, skin diseases, and parasitic diseases), so the results are not always definitive and need to be compared to your allergy symptoms and medical history.

Challenge test

To confirm a food or drug allergy after a skin or blood test result is positive, your allergist may perform a challenge test. For the challenge test, you swallow a very small amount of the suspected allergen (such as milk or antibiotic), usually in a capsule. Real capsules may be alternated with placebo capsules. If there is no reaction, your allergist gradually gives you more until a reaction is noted. Due to the risk of a severe allergic reaction like anaphylaxis, challenge tests are done in a clinical setting and are only performed when absolutely necessary.

Snapshot of a Moving Picture

Most people think of specific allergies in black and white terms -- something you either have or you don't. A study published in the January 2002 issue of the American Journal of Respiratory and Critical Care Medicine emphasizes that the truth is much more complex. Being allergic to something is a continuum -- and that continuum changes over time. Most (but not all!) food allergies get better over time. Most airborne allergies get more common as children get older. Some allergies peak before puberty and then disappear. Others don't even begin until puberty is over.

Furthermore, test results must be interpreted differently at different ages. Under age 1, a positive test is usually a true allergy, but a negative test does not tell you anything. In children over 3 or 4, the reverse tends to be true -- a negative test means the child is probably not allergic to that substance, whereas a positive test does not necessarily mean that the substance causes symptoms for the child.

Most people who do get tested for allergies have a single round of skin testing. This can provide a valuable snapshot of allergies at a single moment in time, but this just "scratches the surface" of a child's long-term allergy story.

Alan Greene, M.D., F.A.A.P.

 

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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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