Skin-prick tests- the standard test for allergy


        SKIN-PRICK TESTS- THE STANDARD TEST FOR ALLERGY
The standard test for allergy is the skin-prick test, which looks at how the skin reacts to a range of common allergens - or to the suspect allergen where the likely cause of the trouble has been identified but confirmation is still needed. Allergen extracts are used, these being prepared from pure samples of foods, pollens, house dust etc. A drop of the extract is placed on the arm, and a prick or scratch made in the skin below the drop. A minute amount of the allergen enters the skin, and if the patient is sensitive to the allergen there will be a marked reaction, known as a wheal-and-flare response.
Skin-prick tests work well for some types of allergen, particularly inhalants. But where the allergen is found in food, they often do not produce a positive result, except in cases where the patient's reaction to the food is immediate and violent.
Skin-prick tests can be negative even though there is a genuine allergic reaction, simply because the reaction is localized - in the gut, nose or wherever. IgE antibodies can often be demonstrated in the part of the body that is affected, but they have clearly not entered the bloodstream, which is why they are not present in the skin.
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Allergies

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