Working out if it's an allergy

Foods can upset people for many reasons. If you break out in hives, or wheeze or vomit after drinking milk, you probably have a milk allergy. But if you feel bloated or get an upset stomach, you probably have lactose intolerance. (See Allergy or intolerance?)

You need to find out whether the symptoms are those of an allergy or an intolerance, so that you don't unnecessarily restrict your or your family's diet or pay for tests that won't make any difference.

The gold standard for diagnosis is a double-blind placebo-controlled food challenge. But because this is time consuming and needs to be carried out in a hospital setting, it isn't always practical.

Your doctor may refer you to an allergy clinic. An allergy specialist (immunologist) will take a clinical history, do a physical examination, and test for allergy.

Testing procedures

Skin prick and RAST (radioallergosorbant) tests are the main medical testing procedures.

The skin prick test involves small drops of potential allergens being placed on your arm (or back, if you're a small child). A tiny prick is made in the skin so the allergen comes into contact with the tissue. A red and raised area will develop around the drop you're allergic to.

In a RAST blood test, a blood sample is mixed with a food extract and the levels of allergic antibody are measured. This test indicates you are sensitised to an allergen, but it may not necessarily mean you'll have an allergic reaction.

Alternative practitioners promote various tests, although orthodox allergy specialists say these tests are inaccurate and don't have any scientific basis. Unproven tests include applied kinesiology (muscle testing), hair analysis, iridology, and pulse testing.

Unfortunately, there aren't enough allergy specialists in New Zealand to manage the burden of allergic disease and there's still a long waiting list to see one in the public hospital system. If you have health insurance with specialist cover, you may be able to claim for the cost of your consultation and tests.