Why vomiting now is probably not the chestnut
Water chestnuts are non-toxic to dogs, and a single raw one at this size wouldn't typically trigger vomiting. The timing suggests something else irritated your dog's stomach — perhaps gulping it whole, or the chestnut's hard texture scraping the throat on the way down. A one-time vomit with no other signs is more likely a mechanical issue than poisoning.
Since your dog is small, even harmless foods can overwhelm the stomach if eaten too quickly. Check the vomit for undigested chunks — if the chestnut came back whole, that confirms it was simply too much at once. Withhold food for two hours, then offer ice chips before trying a teaspoon of plain boiled rice.
When to suspect something unrelated
If your dog had been quietly chewing grass before this, or if you found other scraps near the chestnut, those could be the real culprits. Dogs often vomit from eating too many fibrous plants, spoiled food, or even their own fur — all common in households where pets scavenge.
Watch for specific red flags: vomiting more than twice in an hour, drooling as if nauseous, or trying to vomit but producing nothing. Those warrant an immediate vet call, as they suggest obstruction or illness unrelated to the chestnut. Otherwise, normal energy and interest in treats mean this was just a passing upset.
The next few hours with a 5 kg dog
Small dogs dehydrate faster after vomiting, so focus on hydration first. Wait until thirty minutes have passed without retching, then offer a tablespoon of water every twenty minutes. If that stays down, you can gradually increase the amount over the next two hours.
Skip the next regular meal — an empty stomach helps reset digestion. When reintroducing food, start with a bland mix like one part boiled chicken to three parts rice. The goal is to confirm the stomach can handle simple nutrients before returning to kibble.
Texture matters with raw chestnuts
Raw water chestnuts have a crisp, almost woody texture that some dogs struggle to chew properly. Your dog may have swallowed sharp fragments that irritated the stomach lining on the way down, explaining the delayed reaction. This mechanical irritation isn't toxicity, but it can still cause discomfort.
Next time, try slicing the chestnut thinly or lightly steaming it to soften the cell walls. Either method makes it easier to digest while preserving the mild flavor dogs enjoy. Just remember: even safe foods can cause issues if the portion overwhelms a small dog's digestive capacity.
The full verdict, portion guidance and serving notes are collected on the Water chestnut food facts page.