I had a dog (mixed breed) in which severe and frequent seizures turned
out to be caused by dye in a food product, and it didn't take much of it
either. She only got a dog biscuit a week, when we were visiting my
elderly friend, who loved the dog and kept biscuits there as a treat for
her.
After that I was extra vigilant about antyhing she ate, pretty easy in
my situation as I mostly can feed right off the place. But when I was
traveling or whatever I took all her food along and made sure she got no
treats from anyone, etc.
Took 3 vets to get it figured out, but once we made sure she never got
anything with dye in it, she never had another seizure. Never knew, nor
tried to figure out what dye it might have been, found it easier and
likely safer, just to eliminate all.
Sure pointed up one of the potential problems in food additives, for man
or beast. I figure it can't hurt to avoid dyes (and a lot of other
things, now!), so we do......