Trix has food allergies.. it's common in her breed and she might outgrow it..

The only way I figured it out with Trix is I switched her food to Nature's Recipe and Lamb & Rice Rollover... we've been 'food-induced' sick-free since December 27th.

I'm with Phred on the fact that there really is no test for it EXCEPT for switching the food.... It's all trial and error..

I'm not sure if Rollover is available in your area, but here is the link to their website .. If you wish, I will gladly get a small bag of treats and send them to you to 'test'.. She (and I ) likes their chews because they are 100% digestible.

I also like the fact there is no corn (or soy, or meat meal) in their rolls because Tibbies can't have corn or corn derivatives..