Sudocrem is it steroid cream? Can I apply on my son neck line cause it seem to be red and skin peeling?

How old is your son? Is the cream prescribed for him? It sounds really strong and if it's not meant for your son, then best to avoid it for now. Anything with steroids sounds really strong and harsh. If the skin is peeling and red due to sun burn, may I suggest aloe vera gel -- it really soothes and help with sunburns. And most importantly, it is easy on young skin.