My husband used to scratch his legs until they bled, he tried loads of creams and tablets, then I heard that Aspartame was bad for you.
We checked all labels and he omitted it from his diet, within 48 hours he noticed a difference. Even now if he has some by mistake the itching starts again.
Aspartame is an artificial sweetener, it does have an E number as well as other names, Google there is an American site which shows it can cause just about every illness known to man, but it does give facts and stories about people.
Try omitting it for 2-3 days if no different go to the doctors.