I’ve heard that...
I can buy a home test kit to diagnose food allergies
Yes, you can buy home test kits but I don’t recommend using them. They’re often of a lower standard than those provided by the NHS. Also, allergy tests should be interpreted by a qualified professional who has detailed knowledge of your symptoms and medical history.
If you do buy a home test kit and the results show that you’re allergic to something, go and see your GP to confirm the diagnosis.