I have exactly the same thing happen to me whenever I eat anything. The only thing I can eat without it happening is ice-cream or fruit! This however doesn't just occur when eating, it can happen anytime, anywhere. At first I thought it was stress or anxiety although I have nothing to be anxious about. But it can happen if I'm reading a book, watching television, talking to friends or family. It started around 12-18 months ago however it is now totally out of control. I have been to the doctors and had blood tests including allergy tests and all has come back clear. I just don't know what to do next but there must be some medical explanation. It's not anxiety and my doctor doesn't think so either.
Sounds to me like a slight allergic reaction. Doesn't sound bad though. But when you say your not allergic to anything... How are you certain? You can develop allergies to certain things as you get older or vice versa. My wife used to break out in hives after eating cheddar cheese... This year for some reason her reaction has stopped. Strange I know.
But what you can do is go to the dr and they can do a very simple allergy test and tell you what you are allergic to.
Good luck. Whatever you do, don't worry too much about it. Worrying is no good LOL. I should know... LOL.
How are you sure your not allergic to anything?