Can food intolerance be proven even if I have never eaten the respective food or have not eaten it for a long time?

In order for the nutrition test to detect food intolerance, the food must have been in contact with the respective food at least once in the last few weeks. During food intake, the body produces antibodies depending on the (in)tolerance. If a foodstuff has never been eaten or has not been eaten for a long time, then no or fewer antibodies can be measured in the blood.
If a food has not been eaten for a longer period of time (at least 6 months), the concentration of antibodies in the blood is usually also lower. This means that the test result can also reflect a weaker reaction. However, the level of antibody concentration and the duration of the antibody degradation process varies greatly from person to person.