Allergy tests are performed in order to determine which substances cause allergic reactions in an individual. This can be done through skin tests or blood tests.
Allergy tests are administered in order to detect the allergens that trigger allergic reactions in an individual. Skin prick tests are done to determine airborne allergens such as pollen, mold and dust. Food allergy testing also involves skin prick tests for identifying certain foods that cause allergies such as peanuts, milk, fish or soy. Allergies reactions to insect venom or medications can also be determined in this manner. Blood tests are done when the individual is unable to have a skin test done. This can be the case if the individual is suffering from skin conditions such as eczema, if he has experienced an intense allergic reaction, if his skin tests have shown allergies to many foods, or if he is unable to discontinue taking certain medications that may interfere with the skin allergic reaction.
Certain medications can influence the results of a skin test and as such the doctor must be informed about this.
Skin tests involve placing a small quantity of the allergen on the skin of the individual to determine if an allergic reaction takes place and can be done in three ways. An allergy prick test is done by pricking the skin with a needle after placing a small amount of a solution in which the suspected allergen is contained. This allows the allergen to penetrate the skin. Intradermal testing is done by injecting a small quantity of the allergen-containing solution in the skin. A skin patch test is done by placing a pad containing the solution on the skin and taping it to the skin for a specified period of time.
Blood tests are done to detect the presence of antibodies in the blood. This involves obtaining a sample of blood from the individual. The common types of blood tests are the ELISA or enzyme linked immunosorbent assay test which detects the presence of an antibody called immunoglobulin E that is produced in the body in response to particular allergens.
If allergy symptoms such as a wheal of 3mm or larger develops on the skin in case of a skin test, then it means that the person has tested positive to that particular allergen. In a blood test, if the immunoglobulin E levels are four time higher than the normal level, then the test results are positive.
The main risk involved in skin testing is that a severe allergic reaction may occur which can produce some serious symptoms. Blood tests do not carry any risk other than a tiny bruise at the site of the puncture. In people with bleeding disorders, there can be excessive bleeding.