Yes, it looks like chicken pox, but he’s had this for over a week now and there are no blisters on his trunk at all. Chicken pox is centripetal, seeking the centre. These are little pustules, possibly from shaving his head with a dodgy razor blade, making tiny nicks which then get infected with staphylococci. Mum has been treating him by applying crushed up antihistamine tablets (Piriton) to the lesions, hence the pink powder. He will be much improved with a few days of cloxacillin by mouth, and general hygiene measures.