Allergy symptoms

[leelapops]

Hiya all. As you most probably know, my almost-3-year-old Border Collie is gluten intolerant. This week, he was ill on Monday, and has been a bit "sloppy" since, although he is very much himself, i.e. mad! He is also scratching and biting himself excessively. He will be going to the vet before the end of the week, but I wanted to know what others thought it could be. I've read around, and I wonder if it's another allergy, as that's what his symptoms point to the most.