Help needed with a 5 year old

I’d back Pam up here Jammy. Go and see your doctor. It may be nothing but your son may have an aversion to food additives, in which case a strict control of his diet, or even diabetes (like my wife) another indicator here is how often he needs to visit the loo (because of all the fluid being drunk). In any event knowing is better than not because you then take back control for your sons condition.