My 4-month-old puppy found and swallowed one whole hazelnut — is this an emergency?

It's not typically an emergency, but it warrants close watching. Hazelnuts themselves are not toxic, but a whole nut is a serious choking hazard and can cause intestinal blockage, especially in a small puppy with a narrow gut. The high fat content can also trigger pancreatitis, which is painful and dangerous. Monitor your puppy carefully for the next 24-48 hours for signs like gagging, lethargy, vomiting, loss of appetite, or difficulty passing stool. If you notice any of these, contact your vet immediately.