Dogs experience the world mainly through smell, and their sense of smell is far stronger than ours. They are especially drawn to areas like the crotch or armpits because those parts of the body produce stronger scent signals. Through those scents, a dog can pick up clues about a person’s identity, mood, health, and even physical changes.

This behavior comes from canine social instinct. Dogs use scent to learn about each other, and because they see humans as part of their social world, they often treat people the same way. That is why they may become even more interested when someone is stressed, sick, pregnant, or otherwise giving off a different scent than usual.

Even though the behavior is normal for dogs, it can still be redirected with training. Teaching commands, rewarding more polite greetings, and giving dogs other ways to use their noses can help manage these moments. In the end, this habit is not about bad behavior, but about a dog using its strongest natural sense to understand the world around it.