Allergies are cumulative. If you are allergic to six things you can be exposed to five of them and have no reaction, however the addition of the sixth one could throw you into a sneezing fit. It made sense to reduce the amount of things in my life that cause an allergic reaction. I went to a naturapath recommended by a friend, to have my food allergies tested. The cats I knew about.
Food allergies are much more subtle.
The doctor received no results from the first blood sample he sent to the food allergy test lab. My white blood cells were so sluggish they didn't respond to the tests, a first for him. I took some vitamins to try to build up my blood, then had another test. This was more successful. It returned a list of twenty-one foods that my body thought were foreign.