- If a reaction occurs every time a food is eaten it is more likely to be a true food allergy
- In delayed allergy, because of the long delay between eating the food and having symptoms it is much more difficult to pinpoint whether the food causes an allergy every time it is eaten. For this reason a food diary is recommended
- In a food diary, every food that is eaten is written down (in detail with all ingredients) and reactions also written down, so that a doctor or dietician can look at the diary and see whether a specific food might be related to reactions
- This is especially helpful where one foods exist as a “hidden ingredient” within other foods
Unlike immediate type (IgE mediated) allergies, where skin prick tests and/or blood tests (which detect IgE antibodies to various foods in the blood) may be useful, there are no useful laboratory tests for a delayed type food allergy.
The diagnosis of delayed type allergies relies on stopping to eat that food for a few weeks. If symptoms go away it is then critical to reintroduce that food to prove that symptoms come back.
The reason that a reintroduction challenge must be performed is because the symptoms of delayed type food allergies come and go, and it may be coincidence that symptoms happened to get better when a food was removed.
This is NOT the same as a food challenge test done for immediate type reactions. Because there is no risk of an immediate severe reaction, it can be just reintroduction of a normal portion of the food, and does not need to be done under special conditions.
Remember that “elimination-challenge testing” is not done lightly! Avoiding any food, even for a short time may be difficult, expensive and lead to minor or major nutrition issues. It is always important to have a dietician trained in allergies to guide the process, and this is mandatory when more than one food is involved.
In some types of delayed food allergy a biopsy specimen of the gut may be required.
There is absolutely no evidence that ALCAT, Vega testing, pulse testing or kinesiology are of any benefit in diagnosing food allergy. People who use these tests may spend a lot of money to receive an incorrect list of foods to avoid and risk their nutrition.