L.B.
Hi S.,
I personally had the same thing happen to me and it turned out to be a vitamin D deficiency. I started taking a D supplement and my skin has stopped peeling. You can have his levels tested with a simple blood test and then supplement or just start him on some cod liver oil NOrdic Naturals makes a childrens DHA that is a good source of Vitamin D. Also just 15 minutes per day without sunscreen fully clothed helps the body produce vitamin D.
Take care L.