Each person is able to recognize their own scent thanks to the major histocompatibility complex (MHC), a unique combination of proteins similar to that used by animals to recognize their partners. These are the results of a study published in the journal Proceedings of the Royal Society B , the first to show that humans do indeed ‘smell’ ourselves.
The peptides of the MHC complex are found on the surface of almost all cells in the body, and they help our immune system to differentiate them from the cells of pathogenic organisms. In addition, these molecules also contribute to communication between animals and numerous studies carried out in fish, mice and people have shown that we prefer the smell of individuals with MHC genes different from ours .
In this new study, the researchers recruited 22 female volunteers to whom they applied different perfumes to their armpits. Except for smokers and those with colds, all women preferred to wear perfume that contained a synthetic blend of their own MHC proteins .
To check what was happening in the brain, the scientists performed another test in which they obtained an MRI image of several women who had to smell different solutions. “A very clear difference was observed between the response to self and foreign peptides”, explained Thomas Boehm, author of the study and researcher at the Max Planck Institute for Immunobiology and Epigenetics (Germany). “There is a particular region of the brain that is only activated when a person smells peptides similar to the MHC molecules themselves.” In the same way, when the volunteer smelled foreign molecules, the same area of the brain was always activated.
This work confirms the idea that we prefer to use perfumes that amplify the signal of our CMH, whereas, when we smell other people, we like those that use scents that amplify the CMH signals different from ours. The next step, Boehm explains, “will be to identify the nasal receptors that identify these peptides in humans.”
