I got the notion somewhere that since FPIES is not a classic IgE mediated allergy, the sensitivity threshold is likely to be higher. As in, I don’t need to worry about cross contamination, or cooking fumes, and perhaps could even get away with small quantities. This notion hurt me quite a few times.
I don’t know if there is research on such sensitivity levels generally, but my guess is that it is highly individual. Even some lucky(?) people with IgE mediated allergy can have high thresholds approaching almost a serving of the offending food.
For me, the provocation dose seems low enough that practically speaking I need to avoid my triggers strictly to avoid symptoms. But I can afford to take small risks with cross contamination as trace amounts are unlikely to cause the full blown reaction. It can still make things pretty miserable with multiple trips to the bathroom, etc.
My issue with shrimp perhaps shows an example of the sensitivity level possible with FPIES. If I actually eat a piece of shrimp, pain starts after about a half hour and the most severe symptoms of shock and vomiting occur in about two hours. About a teaspoon of fermented shrimp in soup caused similar reactions that were just a tad milder and delayed and peaking in about four hours. In another incident I had trace amounts of shrimp in broth for dinner and became increasingly uncomfortable during the night with extreme abdominal distension. I could barely sleep and by morning I couldn’t get into my clothes and looked perhaps 6~7 months pregnant. Finally at mid morning diarrhea started and I spent the next hour taking ten plus trips to the restroom. For the next couple of days I had tiny bumps all over my skin. But on the bright side, I didn’t have to fear death with the shock or vomiting.
The pattern I’ve noticed is that the smaller the quantity the more delayed the symptoms. And while they are a tad milder they can still be pretty severe. So it seems for all intents and purposes any and all form of shrimp must be avoided.