How long after ingestion of allergen can reaction occur?
We just tested my nearly 4 y.o. by feeding him pb at my MIL's. His older brother is severly allergic to pn and tn. He had no apparent reaction. Until 8 hours later. He ate food after that -just some nut-free crackers and then went swimming a couple hours after that. No problems. Then, about 8 hrs. later, after eating dinner, I noticed him scratching but thought he had a side ache or was pulling up his pants. We got home an hour later and after his shower, there were massive hives all over his waist and spreading fast over his whole body, which tells me it was a systemic reaction, not localized. I gave him Benedryl and will be checking him every two hours tonight and giving more Benedryl every 4 hours round the clock.