Both are equally good. The skin-prick test is much less expensive but exposes you to potential allergens. The blood test doesn’t expose you to allergens so you have no risk of a bad reaction, but it is more expensive.

I have had both tests done. The skin prick test is supposed to be more sensitive to actual allergies, but it makes you feel tired and run-down afterward. You also run a risk of a severe reaction. In addition, if you take certain medications, such as antihistamines, you have to stop taking them for a day or so beforehand, even if that means you will risk an allergic reaction.

The blood test has improved over the years and, of course, poses no risk at all of setting off an allergic reaction. However, it will show any antibodies remaining in your system, even those developed for allergies you no longer have. In other words, the blood test tends towards false positives.

As Wikipedia puts it:

“RAST often are used to test for allergies when:

• a physician advises against the discontinuation of medications that can interfere with test results or cause medical complications;
• a patient suffers from severe skin conditions such as widespread eczema or psoriasis; or
• a patient has such a high sensitivity level to suspected allergens that any administration of those allergens might result in potentially serious side effects.”