Have you prepared him for that fact at all?
All men are bald in my family. My brother started losing hair at 19, he's fine with it now but found it quite traumatic when so young. I remember him asking me to buy caffeine shampoo etc to try to help. He mentions now how baldness is one of the few traits that it's OK to name call about, despite it being completely out of the control of the person affected.
Anyway I can see that the best approach is to embrace your baldness, and lots of bald men look great - but wondering if I can help my son who is only 10 get towards that confidence.