Scientists identify how humans detect body odor. The vast majority of our responses to smells remain a mystery

• Researchers have said we now have the science to understand why certain smells seem nice, others nasty.
• They discovered a receptor in the nose linked with smelling body odor and another musky scent.

Scientists say they've discovered two new receptors in human noses that determine whether odors appear foul or fine.

Our perception of odors is essentially created when receptors in the nose detect compounds and relay the information to our brain for processing.

One of the newly discovered receptors, called OR4D6, detects the compound that gives human underarm odor its "characteristic". The other detects the Galoxolide musk found in fragrances, called 3M2H, the study authors said.

Genetic variation affects how a person perceives these scents, they said – for example, almost 25% of people don't smell the Galaxolide musk.

The latest research, published in Plos Genetics science journal Thursday, is the first to connect this phenomenon with a specific receptor, the study authors said.

Identifying receptors responsible for perception of 3M2H and body odor may have implications for malodor prevention, the study authors, including a Unilever researcher, said.

Dr Joel Mainland, a co-author of the research from the University of Pennsylvania and the Monell Chemical Senses Center, said that the findings were also of personal interest – he's unable to smell 3M2H at normal concentrations, per the Guardian.

Matthew Cobb, a professor at the University of Manchester and author of the book 'Smell', who wasn't involved in the research, told the newspaper that the findings provided a scientific basis for what is known intuitively – how people have varying experiences of the quality, pleasantness and intensity of odors, with some unable to smell certain odors at all.

To get the findings, the team cross-examined participants' perception of scents with their genetic code.

They tested 10 odors on 1,000 Han Chinese people in New York City, an understudied population, and then checked the findings for six of the odors in an ethnically diverse population of 364, the study authors said.

Both cohorts rated intensity and pleasantness of the odors on a 100-point scale, they said. The scientists then ranked the odors by intensity and unpleasantness, and compared this to the participant's genome.

The scientists were able to reproduce the results from previous studies that found other receptors and focused on Western populations. For example, they also found the receptors linked to the perception of the steroid androstenone, which can be experienced as the smell of sweet flowers, foul-urine, or was odorless, depending on the individual's genetic make-up.

Mainland said that we're still "surprisingly ignorant" about what all the smell receptors do and how they interact with each other.

"There are another 400 or so receptors to study, and the vast majority of our responses to odors remain a mystery," Cobb said.