Food Allergy Testing
Food allergy testing is important in diagnosing food allergies. There are three main types of allergy test:
- Skin Prick Tests
- Specific IgE Blood Tests
- Oral Food Challenges
Skin prick tests and IgE blood tests can both cause false positive results. Your allergist will use these results along with your medical history to make a diagnosis.
Skin Prick Test
During a skin prick test, a drop of a suspected food allergen is placed on the patient’s skin. Then the skin is pricked through the allergen to introduce the allergen under the skin. If the patient is allergic, a wheal or flare will develop within 15 minutes.
Skin prick tests are best for ruling out allergies, as they rarely have false negative results. They do have a high false positive result, so you may get a wheal or flare even if you’re not allergic. For this reason, skin prick tests are more likely to be use to confirm that the patient is allergic when it’s already suspected.
Allergy Blood Test
Blood testing takes a small sample of blood to test for specific IgE. Each food allergen has a specific IgE.
Like the skin prick test, the IgE blood test has a high false positive rate.
People without food allergies but who have allergic disorders like eczema, allergic rhinitis, and asthma frequently test positive for IgE. Even people with no allergies can have a positive test.
The ability of the test to predict allergies differs for each food type too. Higher levels generally mean that it’s more likely the patient is allergic but the levels are not related to the severity of the allergy.
Oral Food Challenge
Oral food challenges are the best method for determining allergies. They should always be carried out by a doctor.
The test usually takes about a day (4-8 hours) to complete. The patient ingests the suspected allergen in gradually increasing amounts during the day. The food challenge is always carried out in a hospital or clinic with a doctor watching so if there is any reaction, they can start treatment immediately.
If the patients shows no symptoms, then the test is deemed to be negative. This is the most reliable method of food allergy testing.
Disclaimer: The information provided is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis or treatment. Allergy Lifestyle Limited (t/a) Allergy Lifestyle) uses reasonable endeavours to check the accuracy of information provided however no warranty is given that they are error-free. Always seek the advice of an allergy specialist and follow your anaphylaxis emergency care plan.