How Are Food Allergies Diagnosed?

How Is A Food Allergy Diagnosed?

Food allergies are usually easily diagnosed because the reaction is so fast and obvious. Even so, your doctor will probably want to confirm your suspicions with a skin-prick test.

Skin-Prick Testing

In a skin-prick test a small drop of liquid containing the allergen is placed on the arm. The doctor makes a small prick in the skin, under the drop of liquid, allowing a minuscule amount of the allergen to enter the bloodstream. A positive reaction is recorded if a red bump develops soon after.

skin testing for allergies

For accuracy the bump should be compared to positive and negative controls. A positive control is where the doctor perform a skin-prick test with histamine, the substance that plays a central role to allergic reactions. The skin should always produce a red bump with a positive test, if it doesn't, it means the skin is under-reactive and there is no point in testing. A negative control should also be performed. This is where a skin-prick test is performed using saline water. It should produce no bump, if it does, then it means the skin is over-reactive and testing is probably no use either. In both cases, a blood test may be more appropriate.

Make sure the clinic you choose has adequate equipment for anything going wrong. If you are extremely sensitive to your culprit food, you could experience an adverse reaction, even anaphylaxis shock, to a skin-prick test. There are no recorded fatalities, but caution is still advisable. Resuscitation equipment should be on hand (see can allergies kill you?).

Skin-prick tests always require some careful interpretation - occasionally the results are not accurate or produce false results. Tests for soya allergies are notoriously less reliable than for, say peanut allergies. Although all sorts of people offer allergy tests, including alternative healers, it's probably best to get a test done by an allergy doctor who knows how to make sense of the results - the doctor's experience counts for a lot.

See also: What foods cause allergies?

• Got another question? See: Allergy Questions

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