Why overnight spoilage makes this worse than fresh fruit
Left at room temperature, oranges begin breaking down within hours — the white mold spots you sometimes see are just the visible part. Fermentation starts underneath, producing alcohols and mild toxins that turn a normally irritating citrus snack into something far more likely to upset your 6 kg dog's stomach. The vomiting suggests his system is rejecting both the spoiled fruit and the natural citrus oils that dogs struggle to process.
Size matters here — a whole orange represents about 10% of your dog's body weight in foreign material. Unlike larger dogs that might pass it with minor issues, his smaller digestive tract has to work much harder. Watch for additional signs like drooling, abdominal tenderness when touched, or refusal to eat over the next 12 hours — these mean the irritation is escalating beyond simple stomach upset.
When mold exposure needs vet attention
Not all molds are equally dangerous, but certain types produce tremorgenic mycotoxins that affect the nervous system. If your dog starts showing unusual twitching, loss of coordination, or seems hypersensitive to touch or sound within the next 6-8 hours, this goes beyond standard food poisoning. The combination of mold risk and citrus toxicity means even stable-seeming dogs under 10 kg often benefit from vet monitoring.
Hydration is your immediate focus — vomiting risks dehydration quickly in small dogs. Offer ice chips first, then small sips of water once he keeps them down. Never induce vomiting at this stage, as the acidic contents could damage his throat a second time. His stomach has already chosen to eject the problem — your job is helping his system recover without adding new irritants.
The full verdict, portion guidance and serving notes are collected on the Orange food facts page.