Despite the lack of studies, researchers still found that CBD was extremely helpful in alleviating both arthritis and seizures in dogs. If you are seeing any of these side effects in your pet, then you should call your veterinarian to schedule an appointment. Typically, these symptoms arise when a pet is given too much CBD and toxicity has taken place. Just like with any prescription or holistic supplement, CBD also comes with a few side effects. Even though there are side effects, they are very mild and very few.