Regular vomiting.

[Rollmops]

DS has been having regular bouts of vomiting since he was 1-2 years old (he's 5 now). They happen usually when he has a cold and coughs, however, often just out of the blue, sometimes whilst eating. He has no noticeable pain or nausea beforehand, no warning signals.
He is absolutely fine afterwards.
It happens about 1-2 a month, usually in the afternoon.
He has no other health problems, is growing well and doing splendidly in school.
What could cause this?

Could it be asthma? This can cause coughing until you vomit especially after a virus.

No idea but DS vomits all the time. At least twice a month, often more. He has a really sensitive gag reflex and only has to think about something vaguely unpleasant & he's sick. Things like seeing a squashed snail, the wrong bit of food being mixed with something else, the smell (or imagined smell) of something that I can't detect, talking about worms etc.

He's never ill with it though & will leave the table, be sick, then some back and finish eating! My sister used to be the same. I haven't seen his GP.