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Diagnosis

If you think you or your child has a food allergy, make an appointment with your GP.

They will ask you some questions about the pattern of your child's symptoms, such as:

They'll also want to know about your child's medical history, such as:

Your GP may also assess your child's weight and size to make sure they're growing at the expected rate.

Referral to an allergy clinic

If your GP suspects a food allergy, you may be referred to an allergy clinic for testing.

The tests needed can vary, depending on the type of allergy:

Skin-prick testing

During a skin-prick test, drops of standardised extracts of foods are placed on the arm. The skin is then pierced with a small lancet, which allows the allergen to come into contact with the cells of your immune system.

Picture of food allergy skin prick test

Occasionally, your doctor may perform the test using a sample of the food thought to cause a reaction.

Itching, redness and swelling usually indicates a positive reaction. This test is usually painless.

A skin-prick test does have a small theoretical chance of causing anaphylaxis, but testing will be carried out where there are facilities to deal with this – usually an allergy clinic, hospital, or larger GP surgery.

Blood test

An alternative to a skin-prick test is a blood test, which measures the amount of allergic antibodies in the blood.

Food elimination diet

In a food elimination diet, the food thought to have caused the allergic reaction is withdrawn from your diet for 2 to 6 weeks. The food is then reintroduced.

If the symptoms go away when the food is withdrawn but return once the food is introduced again, this normally suggests a food allergy or intolerance.

Before starting the diet, you should be given advice from a dietitian on issues such as:

Don't attempt a food elimination diet by yourself without discussing it with a qualified health professional.

Alternative tests

There are several shop-bought tests available that claim to detect allergies, but should be avoided.

They include:

Many alternative testing kits are expensive, the scientific principles they are allegedly based on are unproven, and independent reviews have found them to be unreliable. They should therefore be avoided.

Questions to ask

If your child is diagnosed with a food allergy, or you're an adult who has just been diagnosed with a food allergy, you may want to ask questions such as: