Son potentially had an anaphylaxic reaction

So on Saturday evening we were having a bbq in the garden with a friend round. My partner had bought some prawns and they cooked those on the barbecue with burgers, sausages, typical foods.

My son is 18 months old and he didn't any of the prawns, but his dad did handle them and then handle sons food. And it was all cooked together using same tongs so lots of cross contamination..

Son finished eating and since it was past bedtime I took him inside to change nappy and get into pyjamas, he was throwing a bit of a tantrum crying and trying to roll away, then suddenly he wasn't anymore and he was making a strange grunting sound and had gone almost floppy. I ran back out into garden with him and his face had turned red and his neck was swollen and it was like he couldn't breathe.

We called 999 but then suddenly it was like he got his breathe back and his colour went back to normal although slightly pale, and he seemed very tired. Ambulance crew still came out and checked all his vitals and said he was fine now and potentially was an allergic reaction. His face had come up in hives too. But since they hadn't witnessed it they couldn't say for sure.

I have an appointment with his doctor on Wednesday but just curious what you all think this sounds like? Has anyone been through something similar?

A shellfish allergy even though he didn't actually eat any? If so how bad would it have been if he did eat them.

Any mums on here who's children do have severe allergies like this? How do you cope with the worry?