Can Dogs Eat Tomatoes?
It depends. Ripe, red tomatoes are generally safe for dogs in small quantities — a slice or two won't cause harm. However, the green parts of the tomato plant — stems, leaves, and unripe green tomatoes — contain solanine and tomatine, glycoalkaloid compounds that are toxic to dogs. Symptoms of tomatine poisoning include drooling, vomiting, diarrhea, lethargy, and in severe cases, slowed heart rate and muscle weakness. A medium ripe tomato has about 22 calories and provides lycopene, vitamin C, and potassium, but there are safer fruits to share with your dog.
Key Takeaways
- Tomatine concentration drops dramatically as tomatoes ripen.
- Dogs with arthritis or joint inflammation may be sensitive to nightshade vegetables (tomatoes, peppers, eggplant) — some owners report worsened symptoms, though scientific evidence is limited.
- Tomato plant leaves can cause contact dermatitis (skin irritation) in some dogs who brush against them in gardens.
Explanation
Tomatine concentration drops dramatically as tomatoes ripen. A fully ripe red tomato contains only trace amounts — roughly 0.5 mg per gram compared to 5 mg per gram in a green tomato. At those trace levels, a dog would need to eat an impractical quantity of ripe tomato to experience toxicity. The real danger comes from green, unripe tomatoes and the plant itself. Dogs with access to tomato gardens are at risk because leaves and stems have the highest concentrations. Unlike grapes, where even small amounts cause kidney failure, ripe tomato flesh has a wide safety margin.
If you share ripe tomato with your dog, keep portions small — one or two bite-sized pieces for a medium dog. Remove seeds if possible, as they can cause mild GI irritation in some dogs despite not being toxic. Cherry tomatoes should be cut in half for small breeds to prevent choking. The acidity of tomatoes (pH around 4.3–4.9) can upset stomachs in dogs prone to acid reflux or with sensitive digestion. If your dog has never had tomato before, start with a single small piece and watch for any reaction over 24 hours. Carrots and apples are lower-acid alternatives.
Tomato-based products are a separate concern. Ketchup contains high sugar (4 grams per tablespoon) and sodium (154 mg per tablespoon). Pasta sauce and salsa almost always include garlic and onion, both toxic to dogs. Sun-dried tomatoes are concentrated and often packed in oil with seasonings. Canned diced tomatoes (plain, no salt added) are the safest processed option if you want to add a small amount to homemade dog food, but there's no nutritional necessity. Commercial dog foods that list tomato pomace as an ingredient use a processed form that's free of tomatine.
If your dog eats green tomato or plant material, monitor for symptoms within 2–6 hours. Mild cases produce drooling, stomach upset, and lethargy that resolve within 24 hours. Severe tomatine poisoning — from eating large amounts of plant material — can cause tremors, seizures, and cardiac effects, though this is rare in dogs. Contact your vet or the Pet Poison Helpline (855-764-7661) if you suspect significant ingestion. Bring a sample of what the dog ate to help the vet assess the situation. Watermelon is a much safer summer fruit option that dogs typically enjoy more.
Things to Know
- Dogs with arthritis or joint inflammation may be sensitive to nightshade vegetables (tomatoes, peppers, eggplant) — some owners report worsened symptoms, though scientific evidence is limited.
- Tomato plant leaves can cause contact dermatitis (skin irritation) in some dogs who brush against them in gardens. Fence off tomato plants during growing season.
- Fried green tomatoes are doubly dangerous — high tomatine content plus the oil and breading. Eggs are a safer protein-rich treat than battered foods.
- Heirloom tomatoes that appear green when ripe (like Green Zebra variety) still contain higher tomatine levels than red varieties — avoid sharing these.
- Tomato juice is mostly safe but high in sodium — an 8-ounce glass contains about 650 mg of sodium, far exceeding a small dog's daily needs.