Why smelling a pine tree can instantly lift your mood
Pine is one of those scents that can change a room and your mood in an instant. One whiff, and suddenly you’re transported to a world of snowy wooded landscapes, twinkling lights, a freshly cut tree losing its needles in your childhood living room. The perfume feels soothing and joyful… but why? It turns out the answer has less to do with what’s inside the tree, and more to do with what’s inside us.
“There is nothing in pine that has a specific, inherent pharmacological influence on humans,” says Dr. Rachel Herz, a neuroscientist at Brown University and an expert in the psychological science of smell.
“The way it works is through learned associations. If I associate the smell of pine with relaxation, then it’s going to relax me. If for some reason I associate pine with anxiety, that’s how it’s going to affect me. If I’ve never smelled pine before and have no idea about it, there won’t be any effect.”
Aromatherapy works, but not as advertised
Pine contains compounds called terpenes, like α-pinene and limonene, which are touted in wellness circles for their stress-reducing and mood-enhancing properties. Aromatherapy brands frequently promote pine essential oils with terms such as “refreshing” and “uplifting,” suggesting that there is something inherently calming about the chemistry of the tree itself.
But this idea does not hold up scientifically, according to Herz. She says that smell perception occurs in the amygdala-hippocampus complex, otherwise known as the primary olfactory cortex. It is this mechanism that generates pleasant experiences around particular scents.
Your sense of smell is the first sense you use when you are born. Video: How do we smell? – Rose Eveleth / TED-Ed
“What I always like to say is that aromatherapy works, but not in the way people think,” she says. “If I have an emotional association around a certain smell, it will be instantly activated when I smell a particular smell. It’s actually more immediate than if there was a drug-like mechanism that would take time to metabolize.”
She added that a person would not need to consciously think about their pleasant associations with pine to experience uplifting feelings. “You could consciously experience that nostalgia, but what’s going to happen first is you’re going to feel that mood lift and that feeling of happiness,” she says. “Then you might think of a memory of a time you went camping when you were a kid, for example, but that’s not necessary.”
Humans, Herz explains, are “generalists,” meaning we can thrive in many different environments. Unlike species that are born knowing exactly what certain smells mean (like which smell signals a predator or poison), humans must learn what a smell means.
“It wouldn’t make sense for us to turn to the scent of pine willy-nilly,” she says. “In certain circumstances, this could actually mean danger.”
For example, if a person’s first smell of pine occurs while being chased through the woods by a voracious coyote, it is unlikely that the scent will evoke a warm mood later.
Festive Wreath vs. Floor Cleaner: The Importance of Context in Pine Smells
Sure, you might feel a spike of happiness when you take an invigorating hike through the forest or hang a Christmas wreath on your front door. But what about when you use pine-scented cleaning products to clean the bathroom or hang one of those pine-shaped air fresheners to alleviate a friend’s chain smoking in your car? Does this make a difference?
It depends on your overall perception of the experience, Herz says. “Let’s say you have an essential oil, a real tree, or a chemical made for a cleaning product. If a person is blindfolded and smells each of these samples, the perceptual experience will be the same,” she says. “Where context really comes into play is in interpretation. If I’m in the bathroom opening a bottle of pine cleaner to clean the toilet, that pine smell will have a completely different connotation to me.”
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In fact, Herz and colleagues conducted a study in which they presented participants with a mixture of two chemicals. The chemicals were placed in identical white jars with black lids and consisted of granules under cotton wool. Participants unscrewed the lids and sniffed the cotton.
In one instance, Herz said she handed the jar to attendees and told them they smelled like Parmesan. She then asked a series of questions about the smell and the sensations it evoked.
“They said it was very nice, very familiar and that they would eat it,” Herz says.
A week later, when the participants returned to do the study again, Herz presented them with the jar containing the same scent — but this time, she told them they smelled like vomit.
“People were like, ‘Oh, that’s disgusting,’ and ‘I would never eat that,'” she says. “They couldn’t believe me when I told them it was the exact same smell. It’s like doing a magic trick.”
Herz argues that even though pine scent does not contain mood-enhancing compounds, its effects on well-being should not be ignored.
“It’s not pharmacology: it’s psychology,” she says. “But emotions are real and they have real physiological consequences.”
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