The side effects of de-worming a cat or a dog are generally mild, but can include vomiting or visible worms in the stool. Detect de-worming side effects, taking the animal back to the vet if they persist, withtips from a certified dog trainer in this free video on pet care. Expert: James Pakman Contact: www.sycamore-stables.com Bio: James Pakman is a professional, certified dog trainer who has been working at Sycamore Stables horse and dog facility in Amherst, Mass. for several years. Filmmaker: David Pakman