If you suspect that you or your child has an allergy, an allergy test can establish whether a) you actually have an allergy and b) what you’re allergic to.
If you suspect an allergy, the first port of call is your GP. If, after discussing your symptoms, your GP thinks you may have an allergy, they may offer a blood test to identify the cause of your allergy. Or they may refer you for testing. Most allergy tests are done in hospital outpatient clinics.
At the allergy clinic, the type of test you’re offered will depend on your symptoms. Possible tests include:
- Skin prick test – this is usually the first test to be done when looking for an allergen. It’s quick, painless and safe, and you get the results within about 20 minutes. Your skin is pricked with a tiny amount of the suspected allergen to see if there’s a reaction. If there is, the skin around the prick will very quickly become itchy, and a red wheal will appear.
- Blood test – this is called a specific IgE test. It’s used to measure the amount of IgE antibodies in your blood that have been produced by your immune system in response to a suspected allergen.
- Patch test – this test is used to see if a skin reaction, for example eczema, is caused by contact with a specific chemical or substance. A small amount of the suspect substance or chemical, such as nickel, is added to special metal discs, which are taped to your skin for 48 hours and monitored for a reaction. This test is usually carried out at a dermatology (skin) department in a hospital.
- Food challenge – also called an oral challenge, this test is the most accurate for food allergies. During the test, you’re given the food to which you think you are allergic in gradually increasing amounts to see how you react. Only one food can be tested at each appointment.