Each person contains at least six million smell receptors inside his or her nose, which themselves are of about 400 different types. In a research published in the Proceedings of the National Academy of Sciences (PNAS), scientists from the Weizmann Institute report a method of accurately characterizing a person’s sense of smell, which they state is an ‘olfactory fingerprint’.

What’s intriguing is that the results of the study are not limited to smell alone – these fingerprints could be useful in the early diagnosis of degenerative brain disorders and as a non-invasive test for donor matching.

What’s It All About?

Each person contains at least six million smell receptors inside his or her nose, which themselves are of about 400 different types. Their distribution is different for every individual, pointing towards the likelihood that each individual might also have a unique sense of smell.

To evaluate their hypothesis, researchers developed a method based on finding how different or similar two smells were from each other.

In the first stage, researchers asked the participants to rate 28 different odors in terms of 54 descriptive words, such as ‘masculine’ or ‘lemony’. Based on these ratings, a complex and multidimensional mathematical formula was developed that determined how different or similar two smells were to the human olfactory sense.

Dr. Lavi Secundo, along with Dr. Kobi Snitz and Kineret Weissler, all members of the lab of Prof. Noam Sobel of the Weizmann Institute’s Neurobiology Department, collaboratively devised the mathematical equation. According to Secundo, the strength of the formula is that it does not require participants to agree on using a particular descriptive verb. Hence, the olfactory fingerprint is strictly based on odor, and not on particular verbs and language.

Deciphering The Results

The 28 odors produced 378 distinct pairs, each having a different level of likeliness. This provided the researchers with a 378-dimensional olfactory fingerprint. With the help of this extremely sensitive tool, the research team discovered that every person did in fact have a unique sense of smell. This 378-dimensional computation alone could be used to ‘fingerprint’ about two million people – 34 odors could identify the unique smelling ability of about seven billion individuals.

The next stage of the study was conducted by Drs. Ron Loewenthal, and Nancy Agmon-Levin, and Prof. Yehuda Shoenfeld, all of Sheba Medical Center. They suggested that such an olfactory fingerprint could also form a link between another uniquely diverse system in our body – the immune system. For example, researchers found that an immune antigen, HLA, used to match donors for organ transplants, was associated with certain olfactory fingerprints.

What Comes Next?

Researchers claim that apart from indentifying individuals, olfactory fingerprinting could also be developed into various techniques yielding other benefits, such as early diagnosis of brain degenerative disorders and non-invasive methods of bone-marrow screening to match patients and donors.

The research work was supported by the Norman and Helen Asher Center for Brain Imaging, the Nella and Leon Benoziyo Center for Neurosciences, the Carl and Micaela Einhorn-Dominic Institute for Brain Research, the Nadia Jaglom Laboratory for the Research in the Neurobiology of Olfaction, the Adelis Foundation, the James S. McDonnell Foundation 21st Century Science Scholar in Understanding Human Cognition Program, the Minerva Foundation, the European Research Council and others.