hi, my son is 1yr old. he has suddenly developed dry patches on his skin. this started from his legs and now has spread on his back and sides of stomach as well. the patch is extremely dry & when i apply oil, dryness goes and a light reddish or a black mark remains. dryness comes again after 3-4 hrs. few of them are circular but some do not have any shape. what could be this and if you pls could recommend a soap for children of this age as well. what moistureiser shud i apply on him after bath