Human olfactory sensitivity varies across geographical locations

Why Our Sense of Smell Depends on Where We Live

Most of us take our sense of smell for granted—until we notice a gas leak, sniff spoiled food, or enjoy the aroma of coffee. This study asks a deceptively simple question with big implications: does where you live on the planet change how keen your nose is? By testing people in cities around the world, the researchers show that smell sensitivity is not the same everywhere, and that geography plays a surprisingly large role in how we experience everyday odors.

Smell as an Early Warning and Daily Companion

Smell is one of our body’s early warning systems. A keen nose can help us avoid dangers such as smoke or rotten food, and can shape what we like to eat, how we enjoy social contact, and even how we feel in certain places. Scientists usually measure smell sensitivity by finding how faint an odor a person can reliably detect, known as their odor threshold. Unlike tasks that require naming or describing smells, this basic sensitivity was long thought to be similar across cultures and countries. Earlier hints, however, suggested that people living in different environments—from big cities to rural villages or rainforest communities—might not all sense odors in the same way.

A Global Test of the Human Nose

To explore these differences more carefully, the researchers organized a large, coordinated project across 19 locations in 18 countries, from Argentina and Egypt to Japan and Canada. Over a thousand adults, mostly city dwellers who had lived in their area for at least six months, took part. In quiet, well‑controlled rooms, they were tested with special odor “pens” known as Sniffin’ Sticks. In one test, the pens contained a carefully mixed blend of common fragrances to measure pure smell sensitivity. In another, they contained eucalyptus, which stimulates both the smell system and a related nerve system that senses cooling and irritation inside the nose. Each person also answered questions about their health, mood, and how important smell is in their daily life, and completed short tasks that probed memory, attention, and language abilities.

Location Matters More Than You Might Think

When the team analyzed the results, one pattern stood out: where someone lived explained a substantial share of how sensitive they were to odors. Depending on the test, about 17–20 percent of the differences in sensitivity across all participants could be traced to geographic location alone. In comparison, all the measured personal factors—such as age, gender, nasal airflow, health complaints, mood, and cognitive scores—together explained only about 2 percent of the variation. People in some cities consistently detected weaker smells than those in others, even after adjusting for these individual differences. This means that a resident of one city may reliably notice faint odors that a resident of another city would miss, even if both are the same age and in similar health.

How Age, Mood, and Mind Play a Supporting Role

Although location dominated, several personal traits still mattered. Older participants tended to have lower basic smell sensitivity, echoing earlier research that shows our nose becomes less sharp with age. People reporting more symptoms of depression were also less sensitive to odors, hinting at links between mood, brain circuits, and the sense of smell. In the test combining smell with nasal irritation, women on average performed better than men, those without relevant health problems did better than those with issues such as chronic nasal conditions, and individuals with stronger short‑term memory scores were more sensitive. These results suggest that smell is tied not only to the nose itself, but also to broader aspects of brain health and emotional well‑being.

Unanswered Questions and Real‑World Impact

What exactly about a location shapes its residents’ noses remains an open question. The authors point to a mix of possibilities: long‑term exposure to air pollution, different indoor and outdoor odor landscapes, cultural habits that affect how often we notice or use smells, and even genetic makeup and ancestry. Their urban samples were relatively young and generally healthy, so the true range of global variation may be even wider. Still, the findings already have practical consequences. If smell sensitivity differs by region, medical tests that screen for smell disorders may need location‑specific reference values. Public health officials might also want to pay closer attention to environmental exposures in places where people’s noses appear to be dulled, and companies that design scented products could consider tailoring odor strength to local populations.

What This Means for Everyday Life

This study shows that our noses are shaped not just by who we are, but by where we live. A meaningful slice of the differences in how sharply people detect smells around the world comes down to geography, with age, mood, and certain aspects of brain function playing smaller but important roles. Inhabitants of different regions are, in effect, tuned to their own local chemical landscapes. Understanding this tuning could help us better protect health, design safer and more pleasant environments, and appreciate the hidden ways our surroundings sculpt one of our most underappreciated senses.

Citation: Reichert, A., Abraham, N.M., Abraham, J.N. et al. Human olfactory sensitivity varies across geographical locations. Sci Rep 16, 9713 (2026). https://doi.org/10.1038/s41598-026-38727-w

Keywords: sense of smell, geographical variation, chemosensory sensitivity, air pollution and health, cross-cultural neuroscience