My dog is foaming at the mouth and has blood in its stool.

Many things cause a dog to vomit and pass blood, and you must find the cause to treat it. At first, unsure of cause, fast and withhold water, give cimetidine for vomiting and bismuth subcarbonate for diarrhea, then go to a vet soon. The following can cause bloody stool: first, swallowing a sharp foreign object that damages the gut, needing X-ray and surgery to remove it; second, bad food or parasites causing acute gastroenteritis, usually with normal energy and appetite, needing deworming plus probiotics and anti-inflammatory medicine; third, parvovirus or coronavirus causing tomato-like bloody diarrhea, vomiting, dehydration, and poor condition, with high mortality and no specific drug, needing prompt hospital care..