I Have Celiac.. Does He?

I really could use some info. I live in the middle of "what's a gluten" land where it takes an eternity to get in to a pediatric dermatologist. I am diagnosed celiac, not DH. My son has had skin issues for a couple of years now. He was initially diagnosed with MCV (contagious water wart type things) but I noticed that they cleared up when he was gluten-free with me. He just spent 5 days at his dad's (eating gluten daily) and he's got a completely different looking rash on his elbows, knees, and ankles.
If anyone is willing to help, lmk. I have pic links I can post.
I just don't know what else it could be.