0 Allergies--try the food and see what happens?

The National Institute for Allergy and Infectious Diseases has issued clinical guidelines for determining who is allergic and to what.

If someone has a reaction within minutes or even hours of eating something, it could be an allergy and justify a physical exam and pinprick test (a bit of the suspected substance is pricked under the skin to see if it forms a red wheal).

If it does, yup, probably an allergy. But maybe not. Half to 90% of allergies are not really allergies.

Now doctors are urged to do a combination of tests—including in some cases, an oral food challenge, which means feeding the patient a little of the food to see what happens.

About 4% of kids under 18—three million or so—reported having allergies in 2007. up 18% from 10 years before.

Milk, eggs, peanuts, wheat, soy, fish, and shellfish are the most common allergies.But there are 170 other foods that can cause reactions.

Blood tests measure immunoglobulin E antibodies—which do not necessarily mean the person would be allergic if eating the food.

The skin prick test—much the same. Kids ie eczema show IgE antibodies to all foods, for example.

Still, at the moment, food challenges are time-consuming and scary—emergency equipment has to be standing by. They also are not covered by most insurance.

Stay tuned.