DS has several serious allergies to different foods. The first stage of his reaction is usually hives and if not contained there it will evolved to lip swelling etc. he has epi pens for this.
Anyway a few times I have noticed the odd hive when no food was consumed and it usually happened in his Gran's house. I thought it must be the cat the only other thing we noticed is that he was often hyper at Gran's place.
Anyway he plays tennis and after one session a while ago he got a couple of hives and I give him the Piriton which has desired effect. Last night after tennis he has two big hives and I gave him the Piriton but on the way home he starts acting very strange saying he couldn't talk and wanting to sit down. He perked up a bit but worried I did a Google and there is such a things as exercised induced anaphylaxis. Funnily enough I get exercise induced asthma so I am beginning to think he has this condition. I find it so difficult avoiding all the foods if I now have to start worrying about him when he exercises I think I will go mad.