When it comes to personal space, many people tend to draw clear boundaries, but the truth is that those “rules” of respecting someone’s privacy don’t really apply to dogs.

Yes, dogs are the best friends a human could ever ask for. Their love and loyalty cannot be matched, that’s for sure, but they also have a few quirky habits that can catch their owners off guard, like their tendency to shove their nose where it clearly doesn’t belong.

Just as they instinctively greet other dogs by sniffing their behinds, they often extend the same curiosity to people. That’s the reason why many dogs, without a second thought, will nudge their nose right into a human’s crotch. It may feel awkward for us, but for them, it’s completely natural. So, why do dogs do it?

What many of us see like an embarrassing invasion of privacy is a dog’s way of getting to know someone better and saying “hello.”

In fact, a dog’s nose is one of the most extraordinary tools in the animal kingdom, and everyone who has ever owned a canine can tell you that.

While us humans have about 6 million scent receptors, dogs have up to 300 million which makes their sense of smell around 10,000 times stronger than ours.

What’s more, dogs possess an additional olfactory organ called Jacobson’s organ (or the vomeronasal organ), located just above the roof of their mouth. This special structure helps them detect pheromones—chemical signals that reveal detailed information about another individual, whether it’s a fellow dog, another animal, or even a human. Since that’s plenty of data to process, dogs’ brains dedicate about 40 times more space to scent than ours do, which is what makes them superheroes of smell, able to track down anything from hidden drugs to changes in blood sugar. With this in mind, it really doesn’t come as a surprise that they make extraordinary service dogs that help the ill and the vulnerable.

So, why the crotch?

Well, dogs sticking their noses in our crotches is rather awkward, but they’re not trying to embarrass us. On the contrary, it’s all about dogs being super-powered sniffers and having instincts they can’t turn off, no matter how much we want them to.

One of the reasons why dogs tend to sniff our crotch is because of sweat glands, specifically, apocrine glands. These glands release pheromones, which carry information about age, sex, mood, and even reproductive status. While dogs have these glands all over, the strongest signals come from the genitals and anus, which is why butt-sniffing is considered to be a canine handshake.

Humans also have apocrine glands, mainly in the armpits and groin, and since armpits are hard to reach, the crotch is the next best information hub for the dogs.

For breeds such as Beagles, Bloodhounds, and Basset Hounds, resisting to smell humans’ crotches is nearly impossible.

What Can Dogs Detect?

During certain situations, the smell humans release becomes stronger. Menstruation, childbirth, or even recent sexual activity can increase the release of pheromones, which makes dogs more eager to investigate. That’s also why they have a thing for underwear.

In his book How Dogs Think, Stanley Coren, PhD, explains how Australian Shepherds were once trained to sniff out cows that had just ovulated, helping ranchers time breeding more effectively. While it hasn’t been scientifically proven that dogs can reliably detect ovulation in humans, they certainly notice changes in body chemistry. This same skill is what makes them useful in medical research, including the early detection of conditions like ovarian cancer.

What Can Dogs Detect?

During certain situations, the smell humans release becomes stronger. Menstruation, childbirth, or even recent sexual activity can increase the release of pheromones, which makes dogs more eager to investigate. That’s also why they have a thing for underwear.

In his book How Dogs Think, Stanley Coren, PhD, explains how Australian Shepherds were once trained to sniff out cows that had just ovulated, helping ranchers time breeding more effectively. While it hasn’t been scientifically proven that dogs can reliably detect ovulation in humans, they certainly notice changes in body chemistry. This same skill is what makes them useful in medical research, including the early detection of conditions like ovarian cancer.