Your sense of smell is your own and different from anyone else's, giving everyone their own unique "olfactory fingerprint," researchers say.

The genes responsible for creating the receptors with which our noses detect scents are about 30 percent different between any two individuals, a study at Israel's Weizmann Institute of Science has discovered.

Starting from that discovery, researcher Noam Sobel and his colleagues have designed a sensitive scent test for that "fingerprint," they report in the Proceedings of the National Academy of Sciences.

"Each person expresses a potentially unique subset of [approximately] 400 different olfactory receptor subtypes," the researchers wrote. "Given that the receptors we express partially determine the odors we smell, it follows that each person may have a unique nose."

To gauge the accuracy of the "fingerprint" test, study participants were asked to rate how well 28 odors such as clove or compost matched 54 adjectives such as "pleasant" or "nutty."

All 89 of the test subjects displayed different and distinct olfactory fingerprints, and the researchers found that each individual in the group could be identified using just seven odors and 11 descriptive adjectives.

The researchers estimates that 34 odors and 35 descriptors would be sufficient to individually identify around 7 billion different individual, or roughly the entire population of the world.

Although considered a finely developed sense, smell is underutilized in our modern world, Sobel says he believes, and many people do poorly when it comes to identifying smells, with smell losing out to vision as our primary sense.

"Given a visual picture of an orange, people know what it is immediately," he says. "But we have shown in our labs that when the only cue is an odor, people are not very good at identifying what it is."

Another finding of the study was that the genetic makeup of the olfactory receptors can change over a person's lifetime, being different from year to year as well as from person to person.

There could be practical applications of the findings, the researchers suggest, such as analyzing a person's distinct olfactory fingerprint to diagnose diseases that can affect the sense of smell, such as Parkinson's disease.

In addition, such a test could be utilized for security purposes, since it would be almost impossible to steal or copy an individual's unique olfactory fingerprint, they say.

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