"We're not as sensitive to odors in winter," she added. "And odors aren't as available to be smelled."
Cold air also stimulates the irritant-sensitive trigeminal nerve, said Alan Hirsch, a neurologist and psychiatrist in Chicago. The trigeminal nerve is what makes you cry when you chop an onion and delivers a hit of spiciness when you inhale a whiff of strong mint.
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When odors stimulate both the trigeminal nerve and the olfactory nerve, the experience of smell becomes more intense.
There is a strong psychological component to our sense of smell, Hirsch added, and what we expect to smell has a big influence on what we actually smell.
In "The Invalid's Story" by Mark Twain, for example, a man is stuck on a train next to what he thinks is a rotting corpse but is actually a box of stinky cheese. So overwhelmed by the smell, he spends too long seeking fresh air on the freezing platform and develops a fever that ends up killing him.
"What you think a smell will be impacts whether you like it and what you perceive it to be," Hirsch said. "So, if you go outside in the winter and you are used to smelling snow or chestnuts in the fire or whatever you happen to smell outside, that's what you will interpret smells to be."