Why Do Dogs Sniff Butts? How Dogs Say Hello

A dog's sense of smell

Dogs experience the world mainly through smell. Their noses hold many times more scent receptors than ours, and a large part of the brain is given over to processing smells. They also have a special organ in the roof of the mouth, the vomeronasal organ, that detects chemical signals such as pheromones.

That means a sniff gives a dog a huge amount of detail we cannot imagine. Two dogs meeting are reading each other's scent signatures, and they can remember those signatures long after the meeting.

What the anal glands tell other dogs

The two small anal sacs beside the anus produce a strong-smelling fluid, and a little is released when a dog passes stool and sometimes when they are excited or frightened. Researchers believe the mix of compounds varies between dogs, which is how one dog can recognize another.

Scientists are still working out exactly what messages it carries, but sex, reproductive status, and emotional state are likely among them. The same glands are why some dogs suddenly smell fishy if they are frightened.

Butt sniffing as a polite greeting

Well-socialized dogs usually greet each other with a curved approach rather than head-on, then sniff the face and move round to the rear. Both dogs normally take a turn, and the whole exchange lasts only a few seconds before they move on, play, or wander off.

This ritual may also help dogs stay calm. Sniffing gives them a moment to assess each other without staring, which in dog language can feel rude or threatening.

When to step in

Watch both dogs' body language. Loose bodies, soft eyes, and wiggly movement mean the greeting is going well. Stiff posture, raised hackles, a hard stare, lip lifting, growling, or one dog trying to sit down or move away means one of them is uncomfortable.

If you see tension, calmly call your dog away and give them space, rather than pulling hard on the leash, which can add to the tension. Keep greetings short on leash, and let shy dogs approach at their own pace.

A well-fitted dog harness gives you gentle control to move your dog on when a greeting goes on too long.

Why dogs sniff people's crotches

Dogs sniff people for the same reason: scent glands. People have apocrine sweat glands concentrated in the groin and armpits, and they carry plenty of information for a curious dog. It is embarrassing but normal behavior.

Teach your dog a polite greeting instead, such as sitting for a pat, and reward it. Give guests treats to hand to your dog when they sit. Avoid scolding, which can make some dogs more anxious around visitors.

When to call your vet

If your dog, or other dogs, suddenly sniff or lick your dog's rear end much more than usual, or your dog is scooting, licking under the tail, or smells fishy, the anal glands may be full or infected. These are quick for a vet to check and treat.

Also book a visit if your dog seems withdrawn, irritable, or reluctant to be sniffed by other dogs, which can sometimes be a sign of pain.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.