Cats and dogs vomit on occasion, often without being seriously ill. You may have noticed your dog vomiting after ingesting leaves during playtime outdoors but goes back about his life as per normal.
However, a pet that vomits, especially several times a day, is lethargic, and lacks appetite needs immediate veterinary attention. It is especially imperative you take your pet to see a vet if you find blood in its vomit or if it is throwing up digested blood. Possible causes include gastric ulcers and swallowing foreign objects. Many veterinarians have reported treating dogs and cats that have swallowed sharp bones, knives, socks, fish hooks, and children's toys just to name a few.
Vomiting or diarrhea can stem from many other causes such as gastrointestinal illnesses or parasitic infections that include hookworms, roundworms, whipworms, or giardia. Note that blood in your pet's stool also indicates something very wrong and your pet should be taken to the vet.
To prevent human exposure to parasites, owners should regularly deworm their pets. This is especially important if anyone in the household has a weakened immune system, such as AIDS, or if small children play in areas where pets defecate.