When it comes to allergies most doctors still will chose skin prick testing over blood tests. The main factor is price and accuracy. Skin prick testing is far less expensive than a blood test and the results are for the most part available on the spot compared to a allergy blood test. Most research also shows skin prick testing to be more accurate than blood tests, although companies who market allergy blood tests claim that new improved tests are just as good as skin prick tests or scratch tests.
Blood tests or RAST type tests are designed to measure the level of IgE anti-bodies as they are introduced to allergens. The greater the increase the more severe the allergy reaction. Originally IgE anti-bodies where labeled with a radioactive substance so they could be measured as allergens where introduced. The RAST test is probably most useful for people who are at great risk to suffering a severe allergic reaction that skin prick testing could result in. This may include infants, the elderly and people with weakened immune systems. The test is marketed by many pharmaceutical companies under several names including CAP, RIST and MAST.
Skin prick and scratch testing involves a small prick or scratch on the patients skin which allow a small amount of the allergen to be introduced. After the allergen is introduced the doctor can note if there are any signs of a allergic reaction on the skin. During the test generally several allergens will be tested on a patients body. This differs from patch testing which the allergen is only held against the skin and is usually used to test for allergens that cause contact dermatitis reactions.
When deciding which allergy test is best for you your doctor is still the best one to ask. If the results are not definitive from one type of test you may have to use another to get better confirmation result.
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