Most unlikely deodorants could help - I'm sure he smells good to his parents who could tell him so. But he needs help of dermatologist whom he might ask about UVB light treatment and Topical Tacrolimus. Both of which (not together) brought long me lasting relief. Tacrolimus expensive but was cheap in long run as I found it so effective.-used only one tube.
Vitamin D worth taking as so many in UK likely borderline deficient.. Many dont get enough sun on skin where benefits have been forgotten in scares of skin damage etc.