Swollen lip - what might have caused it?

[IwishIwasmoreorganised]

Ds1 (8) has woken up with a very swollen lip. Half of his top lip is affected, the rest and the bottom one is perfectly normal.

There are no cuts, bites etc that I can see. The only thing that I can think of that's been different is that he has got a gum shield for rugby and he's been wearing that for short periods to get used to it. He's been doing that for the past3 days though and didn't try it at all after about 6pm last night. He was fine when he went to bed at 8pm. Could he be allergic to it (it's one moulded to him and made by a dentist)? It seems strange that only half of his top lip I'd affected if he is.

I'm thinking I'll give him some piriton, but other than that I'm stumped.

[Glastogirl]

I'd say allergy and Piriton sounds like the right way to go!

[IwishIwasmoreorganised]

Thanks. A quick Google hasn't given me any other clues as to what mother cause might be.