why do cats open their mouths after smelling something

Cats open their mouths after smelling something as part of a behavior called the flehmen response. This behavior helps cats analyze scents more deeply by allowing them to draw scent molecules to a special sensory organ in the roof of their mouth called the vomeronasal organ, or Jacobson's organ. This organ is especially sensitive to pheromones, chemical signals that carry important social information such as territory, mating availability, and presence of other animals. When a cat makes this open-mouth expression, sometimes called the "cat stinky face" or grimace, it is not showing disgust but is carefully smelling and tasting the scent through this additional organ. Opening the mouth opens ducts on the roof of the mouth, enhancing the cat’s ability to process complex chemical information that regular smelling through the nose alone cannot achieve. This behavior is normal and common when cats encounter strong, unusual, or interesting odors such as other cats' urine marks or new objects in their environment.