Before I cut out gluten, a doctor told me I had contact dermatitis, which wasn't too far off the mark knowing what I know now. I would get flare ups all the time, and my life was one long adventure of itchy misery. For a long time I had my baby sister convinced that I was allergic to her.
The skin reaction to gluten is a delayed reaction type. That means symptoms flare up hours, even days after the offending food, and the circulating allergens can persist. You can keep a list if you like, but likely a long list of innocent foods will start looking like the culprit when all that happened is that you ate them within the same itch producing window. I have found that common anti-histamines taken daily will cool the itch. I usually take Zyrtec daily when I relapse, and add Benadryl or Cortisol cream as needed.
For years I was down to about one Zyrtec maybe every other week but the past few months I've experienced a flare up and I've needed it daily. I was sure my body had re-booted because to my knowledge I was still eating gluten free but I only just realized that the yummy honey mustard in the cafeteria was the culprit. It's been 5 days, and I'm down to a zyrtec every other day. From past experience I know it takes about 2 weeks to a month to get my body back to normal.
Things will get better for you too. Read labels very carefully, beware of "natural seasoning" "malt" "other spices", and I've found that I feel like magic and sunshine when the food coloring is gone. When in doubt, don't eat/drink it. And it might feel annoying, but ask people exactly what they put into any dish they serve you. You'd be surprised the flour ridden shortcuts people will use to seem like culinary whizzes when trying to impress a crowd. And lastly, it's not rude to refuse to eat something you don't trust. It's your health, you have a right to not feel crappy just because they feel generous.
Itchiness sucks, I literally feel ya.