I know this isn't MD forum but here it goes.
Where I grew up we were allways exposed to the 3 poison plants ivy, oak, and sumac.
All 3 of these have the same looking rash as chicken pox and/or impetigo. Itching them spreads them.
Mom kept this on hand 24/7/365 its called caladryl. It worked wonders for us when we were boys.
Its pink and sold OTC.
http://www.americarx.com/products/6660.html
Just a thought.
Hope he's feeling better.
Lars