Well, in my experience, most stage makeup is just any regular makeup. Ask your dermatologist what your son should avoid in a makeup, and find makeup that doesn't contain that ingredient. For most cases, there is no special makeup for actors/actresses, except for when you need to do special things like creating an extremely pale face, or wounds, or something of the sort. Figure out what he's allergic to, and try to stay away from it. It seems to me like many makeup companies make makeup that is specifically tailored to theater, as well as "every day" stuff, so as long as you keep in mind that specific ingredient, and always be aware of it, your S should be fine!