Dogs smell your crotch primarily because it allows them to gather detailed information about you through their highly sensitive sense of smell. Dogs have up to 220 million olfactory receptors, compared to about 5-6 million in humans, and a specialized vomeronasal organ that detects pheromones and chemicals that humans cannot sense. The crotch area has a high concentration of apocrine sweat glands, which produce pheromones and body odors that carry information about a person's age, sex, mood, recent activities like sexual intercourse, menstruation, or childbirth, and even health status. This natural behavior is similar to how dogs sniff each other's rear ends to identify one another and assess important social and biological information. In essence, crotch sniffing is a dog's way of greeting and conducting a "background check" through scent.
This behavior is rooted in dogs' natural instincts and their reliance on scent to understand their world, not a sign of ill manners. If needed, the behavior can be modified through training by redirecting the dog’s attention or enforcing boundaries during greetings.
