So I just read about this in Allergic Living and wanted to make sure we have a thread here on it.
The term is used to describe when a food allergic reaction is worse or only happens when an addition factor is present. The most common factors are: exercise, non-steroidal anti-inflammatory drugs (or NSAIDs, including aspirin and ibuprofen) and alcohol. They don't know why it occurs but one idea is the cofactor increase the absorption of the food protein.
Yes, I had heard of this especially WRT wheat and exercise - never knew what the term for it was, though.
Yes, celery (of all things) is another common offender in exercise-related food anaphylaxis, apparently.
I can attest to both exercise and alcohol being POTENT factors which can potentiate the severity of allergic responses.
Also cofactors:
hormonal state, other illness, allergen load.