Can pollen allergies cause diarrhea?

I have an 8.5 year old Shih tzu, whom I've had for 3 years. The previous owner warned me that she had skin allergies and she has been scratching ever since.

Starting 4 months ago, she was having a lot of diarrhea, sometimes with blood or mucus. It would be there for a day or two, I'd take her off food, then ease back in with rice, then chicken, then slowly adding her food. And she'd be fine for a few weeks, then sick again. Now she's not even fine for a few weeks before it starts again.

I have had numerous trips to the vet. We did fecal test, blood test, etc and everything was fine. I tried returning to a food I know did not make her sick, but did't matter. I know she's not getting into food that she shouldn't. Finally I did allergy testing: she is not allergic to any food at all. She is only allergic to three kinds of weed (which makes sense with all the scratching). The doctor is recommending allergy shots with the warning that they may not work.

So I guess my question is this: is it possible that these allergies to weeds are causing my dog's diarrhea? Or is there something else we haven't tried? I'm getting really worried!

Thanks.

-Rachel

[Aleda M Cheng, D.V.M., C.V.A]

I believe that it is unlikely unless your dog is ingesting the weeds.

It could still be food allergies.  There is no 100% accurate test for food allergies since allergy tests depend on IgE levels in the blood and some dog's don't produce IgE to food allergens.  Also,  it is not possible to test for all foods that are found in dog foods.  Dry dog foods that are not kept in air tight containers contain storage mites for which dog's can also be allergic.

The only definitive way to test for food allergies is by performing a food trial.  If the symptoms go away once your dog is on a limited ingredient, novel protein diet for 3 months, than it can be assumed that your dog was allergic to something in the prior food.  To determine what your dog was allergic to you must than begin adding one ingredient at a time to the current diet than wait one week.  If no symptoms return during that time, than it can be assumed that your dog is not allergic to that ingredient.  It is a very time consuming process.

Your dog could also have IBD, digestive enzyme deficiency, bacterial overgrowth in the GI.  or chronic colitis.  Maybe a short course of Tylan powder and probiotics would help?

[Rachel228]

Thanks for the information...it definitely clarifies. I will look into the food ingredients and the Tylan powder/probiotics.