Sunflower seeds — Food safety facts
Feed with care · Dogs · full breakdown on the linked food page
Shelled, unsalted seeds in tiny amounts are fine. The shells are sharp and indigestible.
Short answer
It's usually not dangerous if it was just a small amount of shelled, unsalted seeds. The main risks come from the sharp, indigestible shells, which can irritate the gut or cause a blockage if swallowed. A few plain seeds are generally okay, but the high fat content can sometimes upset a sensitive stomach. Keep an eye out for vomiting or constipation over the next day, and check with your vet if your dog acts unusually.