My 6 year old son might have DH. I just wrote a novel about it here:
http://www.celiac.com/gluten-free/topic/106990-possible-dh-6-year-old/
He has been gluten-free for 3 weeks and after about 10 days we noticed that his older lesions finally started healing and he even went a few days with no itching at all. We got a dermatologist appt much sooner than we expected (April 14 ) and we have decided to give him gluten again so the derm will see the rash as it truly is. We weren't sure how long it would take to flare up again. This is how it has gone so far:
Day one - out for dinner ate a hot dog with bun around 5:30pm, itching by 7:00, including itching on his irritated area that I iodined last week (see my original post...still feeling a little guilty for doing that to him). It hadn't itched at all since the initial day.
Day two - no gluten in am, afternoon extremely emotional crying at a birthday party because the game was "too hard", clingy and weepy for a good hour. Unlike him...but could have been the situation, who knows. Dinner, 2 pieces of bread, bedtime, itchy and scratching until his pj's were bloody 
Day three (today) - 2 pieces of bread at brunch and no reaction. No itching, his body looks good, nothing angry looking. He says he forgot all about it today. Which is great of course, but I was surpised.
Could I be mistaken about the whole DH thing or is it normal for reaction times to vary?