Hi Keerti. Indeed grapes pose a threat of toxicity in dogs but as per the studies some pets might not show any symptoms post ingestion. Immediate vomiting is advisable in such cases. Plz supervise your pet if he shows in signs of lethargy or abdominal discomfort in next 24 hours. To be on safer side, you can even get blood tests done upon clinical examination by a vet as early as possible.