If you have DH you will likely also want to avoid iodine, which is common in seafoods and dairy products, as it can exacerbate symptoms in some people. This article may also be helpful as it offers various ways to relieve the itch:  

I know this super old, but I’ve been having this problem on and off for a few years now but it’s gotten worse. I haven’t eaten gluten in 10 years. I don’t eat dairy, soy, potatoes, rice sesame, or use any kind of spices on my food yet I still get a full body itch. I had allergy testing done all they found were a couple of tree nut allergies nothing else. The doctor pretty much brushed me off and told me everything looks fine. My skin looks like I’ve been burned. I can’t sleep I wake up scratching scratching it’s driving me crazy. Only time it goes away is after a long hot shower. And that’s temporary relief. I’m starting to think I’m coming in contact with something but even with my clothes I use a dye free detergent.  I’m seeing a dermatologist next year so I am really hoping they listen to me and don’t tell me I’m “young” and “healthy” when I’m literally scratching my skin off 

Thanks! It should be quite helpful once I learn how to navigate properly🙏🏻

I've never fainted but do get severe cramps and intractable nausea followed by diarrhea. There's probably a lot of blood flow being diverted to the gut to support all the stressful activity happening there and, coupled with the dehydration that occurs, I can easily see how insufficient blood flow to the brain and fainting could occur. By the way, welcome to the forum, @Mary Em!

Has anyone else fainted after gluten ingestion? Along with the vomiting, diarrhea and chills, I passed out   First time doing that and it scared me.  10 years celiac and I have been very careful but eating out is a gamble.