Glossary

Vomeronasal organ

A small scent-sensing organ in the roof of a dog's mouth and nose that detects chemical signals such as pheromones.

Also called: Jacobson's organ, VNO, vomeronasal gland, second nose

The vomeronasal organ, or Jacobson's organ, is a pair of fluid-filled tubes above the roof of a dog's mouth, behind the upper front teeth. Tiny openings behind the incisors connect it to the mouth and nose. It is linked to a separate part of the brain from the main smell system.

It is believed to detect chemical signals, called pheromones, that carry information about identity, reproductive state and mood, particularly from urine and other body scents. It may be why dogs interested in a scent mark sometimes show chattering or lip movements.

Its exact role in dogs is not fully understood, and claims about "reading minds" or "sensing emotions" with it go beyond the evidence. It is separate from ordinary smelling and does not give dogs a mysterious sense. No action is needed from owners.

Last reviewed November 8, 2026

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Related terms

Sense of smell A dog's main sense, thousands of times more sensitive than ours by some estimates, with far more scent receptors and a dedicated airflow in the nose. Scent work Any activity in which a dog uses its nose to find a target odor, from backyard hide-and-seek games to trained detection jobs. Nosework A dog sport in which dogs search rooms, vehicles, outdoor areas and containers for a specific trained odor and alert their handlers. Dog body language The postures, faces and movements dogs use to communicate feelings and intentions without sound.