Why Do Dogs Kick Their Legs When You Scratch Their Bellies?

Every dog seems to have one—that special spot on his belly or flank that, when scratched, sends his back leg kicking like crazy. It’s odd and amusing, especially because some dogs seems to be as confused by it as their owners are. What’s going on?

Not much more than a response called the “scratch reflex.” If you run your hand over a spot of your dog's skin that’s irritated, or scratch too hard or too lightly, you’re actually being counter productive and creating an itching sensation. Nerves running through the chest and abdomen register your friendly touch as irritation, and the dog’s leg reflexively leaps into action, often haphazardly, to try and scratch the itch.

Aside from being a great way to get a laugh at your pooch’s expense, the scratch reflex is a useful diagnostic tool. Veterinarians use it to test for spinal or nerve problems the same way they tap on human knees with that little hammer. If a dog doesn’t kick at all in response to a thorough belly scratch, the vet has reason to look further into possible nerve damage.

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