My son has developed a rash and it seems to be getting worse. any ideas? it is on legs, feet, hands and face. it's not bothering him. red circles but the inside of these are pale. the ones on his face are different again just small red spots

Doctor can examine: Rashes are hard to describe in words. If the spots don't increase, they might be just bug bites, but those tend to itch. If they keep increasing in number, then they might be hives, which is an allergic reaction and is also itchy. Red circles with a paler center can be a more serious type of hives. Some people feel more itch than other people do. A doctor should examine such a rash.

Viral rash??: Might be possible if otherwise well and widespread rash but very difficult to tell without seeing it. An inperson consult with the GP or a virtual consult with the out of hours service will help us make a diganosis here. If unwell should seek urgent medical attention to rule out potentially serious causes of rash.

Hand, foot and mouth: This could be the classical symptoms of Hand, foot and mouth disease which is caused by the Coxsackie virus. It typically begins with a fever and feeling generally unwell. This is followed a day later by flat discolored spots or bumps that may blister, on the hands, feet, and mout. Signs and symptoms normally appear 3–6 days after exposure and resolves in a week. See you doctor to confirm this.

Viral or allergic?: Hard to say without a picture or more information. But in-reality if it does not bother him and he has no other symptoms it is likely not an issue. If concerned see your GP.