TL;DR: Eating grass and vomiting is usually a natural behavior used by cats to clear their digestive tracts, but you should seek veterinary care if it is accompanied by lethargy or if the grass was treated with chemicals.
Why is my cat eating grass and then vomiting?
- Grass provides cats with folic acid and dietary fiber to aid digestion.
- Nibbling on grass helps move indigestible items, such as hairballs or feathers, through the digestive tract.
- Because cats lack the specific enzymes needed to break down plant matter, ingestion often triggers a gag reflex to clear the stomach.
Is it an emergency if my cat eats grass and vomits?
- Urgency Level: Low. In the vast majority of cases, this is a natural, instinctual behavior and not an immediate cause for alarm.
- Contact your veterinarian immediately if the vomiting is accompanied by lethargy or a complete loss of appetite.
- Seek professional guidance if the grass consumed was treated with pesticides or fertilizers.
How can taking a photo of the vomit help my veterinarian?
- A clear photo of the vomit and the grass consumed provides essential information for remote triage.
- Veterinarians use the photo to examine color, consistency, and the presence of foreign materials or parasites.
- This visual evidence helps determine if the behavior is simple stomach clearing or a sign of an underlying gastrointestinal issue.
Clinical Context (Merck Veterinary Manual)
Vomiting in cats, including after eating grass, can be a sign of dietary indiscretion or intolerance, such as ingestion of novel, spoiled, or contaminated foods or foreign material. Vomitus may contain bile, food, froth, blood, or evidence of an ingested substance like grass. While occasional vomiting may be normal, chronic vomiting should be investigated for underlying conditions such as thyroid, liver, or kidney dysfunction. Diagnosis is usually based on history, clinical findings, and response to symptomatic treatment; however, a specific diagnosis should be sought if clinical signs do not resolve within 2 days, if hematemesis or melena are present, if the animal is systemically unwell, or if abnormalities are noted on abdominal palpation.
Chapter: Pharmacology
Source: The Merck Veterinary Manual, 11th Edition (Page 2547)