“Can cats smell stress?”

The Ten-Year-Old takes Canelo for a tour of our back yard. (Photo: Shala Howell)

I can tell my daughter is growing up because she’s starting to experience a bit of emotional turbulence again. She knows we love her regardless, but sometimes she’s not sure about our cat, Canelo. He is not always patient with her erratic moods.

One afternoon after a rough day at school, The Ten-Year-Old tried to calm herself down by picking Canelo up for a hug. He was having none of it.

The Ten-Year-Old was disappointed when Canelo ran off instead of giving her the reassuring head-bonk she was looking for, but as always, her curiosity won out. “Mommyo, can cats smell stress?”

I didn’t know.

Can cats even tell when we’re stressed? 

Everyone from Catster to the BBC agrees that cats can tell when their owners are going through periods of stress. Some even go so far as to say that our own stress may have a detrimental effect upon our cat’s health. But very few put forth any sort of explanation for why this is true.

In her article for the BBC, Robin Wylie speculates that over time cats become attuned to their owners’ emotional gestures. They connect our smiles with positive rewards–happy owners are more likely to spoil their cats with treats and snuggles. As evidence for this, Wylie points to an admittedly small study of 12 cats and their owners led by Moriah Galvan and Jennifer Vonk of Oakland University in Rochester, Michigan. Published in the January 2016 issue of Animal Cognition, the study found that while cats didn’t seem as attuned to human emotions as dogs, cats were more likely to want to be near their owners when those owners smiled, and to avoid them when they frowned.

Another earlier study, led by Dr. Isabella Merola from the University of Lincoln’s School of Life Science in the UK, tested the reactions of 24 cats when placed in a room with their owner and a strange, anxiety-provoking object — in this case, an electric fan to which plastic green ribbons had been tied. The study found that the cats looked at their owner’s faces while evaluating how to react to the fan.  Cats paired with calm, smiling owners appeared less anxious about the fan, although none of the cats approached it.

These studies seem to show that cats pay attention to our facial expressions, but are our faces really the main source of information for our cats?

Back in the day when I had two cats, Mulberry would scratch and hiss at Cozy when he came home from the vet. When I asked my vet about it, he told me that Mulberry was reacting to the fact that Cozy smelled wrong. Things would go back to normal, he told me, once Cozy smelled like himself again. And they did.

Turns out, cats have 200 million scent receptors in their noses, making their sense of smell by far their most important source of information.

If cats are so sensitive to smell, it seems likely that they may be reacting to the scent of our stress, and not just the facial expression of it.

So, does human stress have a smell?

According to the writers at Healthy Women, three things make a human sweat: heat, exercise, and stress. What’s interesting about this is that the mechanism for producing sweat under stressful conditions is different from the mechanism that produces sweat in reaction to heat or exercise.

Sweat from heat and activity is produced by the eccrine glands, which are located all over our body. They produce a thinner, typically odorless, sweat designed to help us cool down.

Sweat from stress originates in the apocrine glands in our armpits.  Sweat created in the apocrine glands is thicker and full of fat and proteins. The bacteria on our skin love to feast on apocrine sweat, breaking it down into fatty acids and ammonia. That process is why armpit sweat smells so much worse than exercise- or heat-induced sweat.

George Preti, Ph.D. is an organic chemist who researches the origin of human odors at the Monell Chemical Senses Center. In an interview with Men’s Health writer Alisa Hrustic, Preti pointed out that animals also emit an odor when they are stressed. He thinks that odor may act as a warning to their peers that something dangerous is happening.

If we humans with our inferior noses can smell the difference between heat- or exercise sweat and the funky stuff we sweat in our armpits while stressed, I have no doubt our cats can as well.

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About Shala Howell

I spent two decades helping companies like Bell Labs, Juniper Networks, and a genetic testing company that was later acquired by CVS translate some of the world’s most complicated concepts into actionable, understandable English. Now I'm working on a much harder problem -- fostering children’s curiosity and engagement in the scientific, artistic, and linguistic world that surrounds them. The first book in my Caterpickles Parenting Series, What’s That, Mom?, focuses on how to use public art to nurture children’s curiosity in the world around them. My next book, Did Dinosaurs Have Belly Buttons?, is currently planned for release in 2018. In the meantime, you can find me blogging about life with a very curious Ten-Year-Old at Caterpickles.com, chatting about books and the writing life at BostonWriters.blog, and tweeting about books, writing, science, & things that make me smile at @shalahowell.
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