There are several ways in which a formal food allergy diagnosis can be made; all should be made through an allergy specialist doctor, and for children, preferably a paediatric allergy specialist. There are several NHS centres across the UK that now have paediatric allergy doctors and nurses, there is also a rise in the amount of general paediatricians who have a specialist interest in food allergies.
Once you're seen by an allergy specialist they are likely to test your child with a skin prick test - using a small amount of liquid onto the forearm, a small prick is used to introduce the allergen into the top layer of skin. If your child is allergic to the allergen a small hive will appear within 15-20 minutes. If not, no hive will appear. By using this test you will be able to leave the appointment with an understanding of your child’s allergies, as the results will be discussed with you before you leave. Skin prick testing is very safe, but must always be carried out by the trained doctors or nurses within the allergy department.
There is also a blood test that your doctor may request, commonly called a RAST test. This result will take longer (anywhere between a week to three weeks) - both of these tests are used as a guide, and must be discussed with medical staff.