How does it affect the results of my FOOD REACTION TEST if I haven't eaten certain foods in a long time?

The specific IgG4 antibodies can certainly be detected in the blood for a while.
Over time, the concentration decreases, but especially if the concentration is high, it is possible that antibodies are still detectable after many months.
In this case, we recommend repeating the test at a later date to check how the antibody concentration has developed. A sensitivity can recede in the course of life.
That is why, it can be advisable to gradually reintroduce the food into your diet and pay close attention to your well-being and possible symptoms.