Itchless Rash on my son's skin

[mamajah]

My son has some sort of rash on his back. it's NOT red or anything. just seems like extremely dry skin. It's rough to the touch and seems to be spreading onto his whole back. It only started out as little patches of dry skin. (I thought it was just dry skin) but it's starting to spread from his back onto his chest and a little on his arms. His legs also are getting patches of the dry skin. I can't tell if it's a rash or or not because, it's not red, it is almost like the same color of his skin... You can only tell if you look very closely that there are tiny bumps, like sand paper almost. I'm afraid that it may be something I should be worried about. That I my be under reacting and should take him to the Dr. What should I do? I've tried to rub johnson lotion (I've always rubbed his skin with it every night after his bath, and it never gave him rash, so I know that's not the prob) I've also tried hydroquartizone. Doesn't seem to be working. I need help! Please help me!