If you have an allergy, your immune system views the allergen as an invader and a chain reaction is initiated. White blood cells of the immune system produce IgE antibodies. These antibodies attach themselves to special cells called mast cells, causing a release of potent chemicals such as histamine.These chemicals cause symptoms such as:
- Itching in the nose, roof of the mouth, throat, eyes
- Stuffy nose (congestion)
- Runny nose
- Tearing eyes
- Dark circles under the eyes
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- Hay Fever (Allergic Rhinitis)
- Food Allergy
- Drug Allergy
- Latex Allergy
- Stinging Insect Allergy
- Pet Allergy
Prick tests involve applying suspected allergens to the surface of the skin (topically) and then pricking the skin to introduce the substances into the skin. These tests, which usually are performed on the forearm, upper arm, or upper back, allow several allergens to be tested at the same time. Allergic reactions (e.g., itching, redness, swelling) usually develop within 20 minutes. Intradermal tests, which involve injecting a small amount of allergen into the outer layer of skin, may be required to conclusively rule out allergic sensitivities; often used to diagnose hay fever, food allergies, drug allergies and latex allergy.
Patch tests can be used to diagnose contact dermatitis and delayed food allergy. In this test, the allergist/immunologist places a small amount of allergen on the skin (usually on the back), covers the area with a bandage, and checks for a reaction after 48-72 hours. Patients who are allergic to the substance develop a rash, or even blisters, on the skin.
While not done in our office, a physician may order a allergy blood test whichs involves taking a blood sample, adding an allergen to the sample, and measuring the amount of immunoglobulin E (IgE) antibodies produced in response to the allergen.
Allergy blood tests, which are less sensitive and more expensive than skin tests, are usually reserved for rare cases when allergy skin tests may not be accurate (e.g., when the patient has sensitive skin that reacts to a saline prick test or has a skin condition, such as hives or eczema, that prevents an adequate field for skin tests).
For more about our food allergy services please check out our institute’s page at www.foodallergycharlotte.