@ Karen
Just go by what the veterinarian that is treating your dog recommends.
Supplements can cause harm and they can interfere with the absorption of prescription meds (the ones that actually help). Do not waste your money. Discuss with your vet first.
Overview of the Evidence for Probiotics in Cats and Dogs
excerpt below, click on link for full article and comments.
Bottom Line
This review provides a concise survey of the probiotic research in dogs and cats to date, including an appraisal of the significant weaknesses and limitations on the existing studies. The bottom line is consistent with my own view of the literature.
There are few studies, and those that have been done have significant limitations and often conflict.
There is reasonable evidence for some clinical benefit in acute diarrhea associated with stress or antibiotic use.
There is no high-quality, consistent evidence for most suggested uses of probiotics.
The unregulated probiotic products on the market today are plagued with inaccurate labeling and poor quality control. This means that even if probiotics might be beneficial in some cases, it is unclear if the actual products available could achieve these benefits.
There do not yet appear to be significant risks to probiotics, though the evidence for this safety also quite limited.
PS: Re: Chewy https://prime.peta.org/2017/05/buyer-beware-chewy-com-purchased-petsmart/
