Why?
Tomatoes belong to the nightshade family, along with potatoes and eggplant. The green parts of the plant, including leaves, stems and unripe fruit, contain glycoalkaloids called solanine and tomatine, which irritate the gut and can affect the nervous system. As the fruit ripens, those compounds mostly disappear, so ripe red flesh isn't toxic, but it's acidic and offers nothing a carnivore needs.
How much?
One or two small cubes of ripe, washed tomato with the stem removed, once in a while. Plain only: no pasta sauce, ketchup or salsa, which are often salty, sugary or made with garlic and onion.
The risks
- Vomiting or diarrhea after eating green parts or unripe tomatoes
- Drooling, lethargy or weakness if the plant was chewed
- Slow heart rate after eating a large amount of the plant
- Garlic or onion hidden in tomato sauces
- Stomach irritation from the acidity
Your cat ate some: what now?
A bite of ripe tomato is usually nothing to worry about. If your cat chewed leaves, stems or a green tomato, watch for vomiting, drooling or unusual tiredness over the next 24 to 48 hours, and call your vet if they appear or if a lot was eaten. If it was a sauce made with garlic or onion, call your vet right away.
Better options
If your cat enjoys something fresh and crunchy, cucumber or zucchini are simpler, with no toxic parts to worry about. A bite of plain cooked chicken beats both.
Common questions
Can cats eat cherry tomatoes?
The same rule applies: a ripe cherry tomato cut into quarters is fine in small amounts. Pull off the green stem and cut it up so it can't be swallowed whole.
Are tomato plants toxic to cats?
Yes. The leaves and stems contain solanine and can cause drooling, vomiting, diarrhea and lethargy if chewed. Keep tomato plants out of reach, especially indoors or on a balcony.
This information is general and does not replace advice from a veterinarian. If your cat has swallowed something toxic, call your vet or an animal poison control center right away, without waiting for symptoms.