Ask Anything: Why do things smell different in warmer weather?

Summer is coming, bringing with it blossoming flowers, sun, and a million baby rabbits who seem to have sprung out of the ground. With the joys of summer you may also notice a stronger stench from the trash bins outside your house, or finally confirm that your neighbor does have a cat because you can most definitely smell the litter box from across the hall.

The smells that seem to only appear in warmer weather don’t disappear in the winter, it’s just harder for them to reach our nose when it’s cold outside.

“Smell is a physical sense composed of the human body being able to detect the presence of chemical molecules,” Dr. Pamela Dalton, co-chair of the Monell Chemical Senses Center Postdoctoral Training Program, says. “Those chemical molecules have to be small enough and light enough to actually fly up into the air because if they can’t be inhaled into our nose we won’t smell them.”

And what is likely to bring the odor molecules of your neighbor’s litter box straight to your nose? Heat, Dalton says.

“The molecules tend to stay more attached to the surfaces that they’re on,” Dalton says. “When you warm up the surface with sun, you’re releasing them from that surface.”

Colder temperatures can prevent odor molecules from making it to your nose, but they may also impact the normal smelling functions of your nose. Dr. Richard Axel, MD and professor of biochemistry at Columbia University, published a detailed article in Scientific American in 1995 explaining the details of how we smell.

“An odor is first detected in the upper region of the nose, as the olfactory epithelium,” Axel wrote. “In this area, odor molecules bind to receptors on hairlike projections, or cilia.”

This process is necessary for smells to register in our brains, but in the winter it may be somewhat inhibited, Dalton says.

“When we [grow olfactory neurons] during the winter months the neurons are much harder to find because they’re buried deep in the epithelium,” Dalton said. “It’s almost like they’re putting on their winter coats and trying to be protected.”

In addition, the dry air of winter may impact the olfactory senses.

“There is less direct evidence for it,” Dalton adds, “but it appears that our noses work better when they’re well humidified and warmer. The more humid and wet and moist the environment is around the receptors, the better the molecules are able to travel through the mucus to attach to the receptors.”

So if you’re trying to lose the cat smell you have a variety of options to try: an air conditioner, a fan or asking your neighbor to get rid of their pet.