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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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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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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. |
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.
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