Is Star Fruit toxic to dogs?

Soluble oxalate salts are absorbed from the gastrointestinal tract and bind with the body's calcium, causing a sudden drop in calcium levels and potential acute renal failure.

Your vet decides whether to make your dog vomit. For soluble oxalate plants, the Merck Veterinary Manual describes decontamination (making the pet vomit, then one dose of activated charcoal with a laxative) followed by a drip (IV fluids) for 24 to 48 hours. If blood calcium drops, the vet gives calcium gluconate into a vein, and checks kidney values while your dog is in hospital. VETgirl adds anti-nausea medicine, blood and urine tests for low calcium, oxalate crystals and kidney injury, and more aggressive treatment for pets that are dehydrated or have chronic kidney failure. The two dogs in the 2019 report received activated charcoal, IV fluids, anti-nausea medicine (maropitant) and oxygen through a face mask, and stayed at the clinic for 24 hours. They were then prescribed an acid reducer (omeprazole) and an anti-nausea medicine (ondansetron), in case they vomited.

No outcome figures for dogs were found. The Merck Veterinary Manual says exposure to soluble oxalate plants is not common in companion animals, but life-threatening signs may occur. VETgirl says kidney injury from these plants is generally thought to be rare. Both dogs in the 2019 report improved markedly with treatment, had normal vital signs at a check the next day and showed no relapse, and the authors describe the outlook in their case as favorable. Blood tests showed a raised liver enzyme (ALT) in both dogs, which the authors suggest may point to liver effects of caramboxin, another toxin in the fruit. Their kidney values were normal. None of the sources we checked describes a death in a dog.

• Star fruit (Averrhoa carambola), also called carambola or five-finger. The fruit has a thin, waxy, light to dark yellow skin and five ribs, so slices are shaped like stars.
• Kitchens. Star fruit is mostly eaten fresh. It is sliced into fruit salads and used as a garnish on meat, salads and casseroles.
• Sweet and sour kinds. There are two main types of star fruit, sweet and tart (sour). Sweet types are recommended for eating fresh, and both types are used in cooking and home recipes. The Merck Veterinary Manual and Pet Poison Helpline name sour star fruit as the dangerous kind: Pet Poison Helpline says it contains dangerous concentrations of soluble oxalates.
• Garden trees in warm climates. The carambola tree is grown in tropical and warm subtropical areas around the world, and in the US it is grown commercially in southern Florida and Hawaii. It is a small to medium evergreen tree, 7 to 10 m (22 to 33 ft) tall. In south Florida, the harvest season generally runs from June through February, and a few fruits are usually available all year.
• Related plants. Star fruit belongs to the same plant family as shamrock (Oxalis). The Merck Veterinary Manual lists shamrock, sorrel and dock among the other plants that contain soluble oxalates, and Texas A&M AgriLife Extension adds rhubarb leaves.

• Don't share star fruit with your dog or cat. The two dogs in the 2019 report fell ill after their owner gave them some.
• Keep fruit bowls, fruit salads and dishes garnished with star fruit out of your pets' reach.
• If you grow a carambola tree, keep your dog from eating its fruit and pick up fruit that falls. In south Florida, the harvest season generally runs from June through February, and a few fruits are usually available all year.
• Take extra care if your pet has kidney disease. Pet Poison Helpline's note that sweet star fruit isn't poisonous applies only to pets with healthy kidneys, and VETgirl says pets with chronic kidney failure or dehydration may be more at risk.
• Keep shamrock plants (Oxalis) out of reach too. Like sour star fruit, they contain soluble oxalates, according to the Merck Veterinary Manual and Texas A&M AgriLife Extension.