Sounds awful Steve.....glad to see your still around though.

I don't about others but I too have had similar experiences and it's not nice.

Doc Alan is right......you should take steps to discover what's likely to have been the cause. Why not talk with your GP and see if there are any tests that can be done. If it's really something like a nut allergy you need to know for sure so you can take appropriate precautions.
I remember you recently had a health check MOT with blood tests etc and all was OK.....
Does no harm to get another one though.

Stay healthy mate