Past research has demonstrated that each mammal individual has a certain smell that separates it from its peers. This comes in very handy for a large number of animals in a vast series of actions, such as choosing companions for mating purposes, or delimiting one's own territory. The odor is eliminated by means of body fluids, such as sweat or urine, and that is why you often see dogs or other animals marking their territory.

The uniqueness of the individual smell is developed by the genes located in a zone called “the major histocompatibility complex” (MHC), which has an important functionality in the immune system of most of the vertebrates. More specifically, the odor is contained in those chemical molecules of the fluids called volatile organic compounds (VOCs), but it can be altered by external factors, such as some elements in the food consumed by the mammal (like when people ingest garlic or meat regularly and in large amounts).

Starting from this fact, scientists from the Philadelphia-based Monell Chemical Senses Center wanted to find out whether the diet changes could effectively alter an individual's natural odor up to the point where they could no longer be recognized by peers. Their tests on mice (who were taught to distinguish between pairs of mice with different diets and/or MHC genes) revealed that, even though these changes indeed affected a significant part of the animals' odor, the natural smell ultimately still persisted, allowing the test mice to be recognized as usual.

The testing of this theory on humans, with consequent positive results, could provide an alternative tool for individual recognition, besides the regular fingerprint-based one. According to Gary Beauchamp, a behavioral biologist at Monell and one of the conductors of the research, “The findings using this animal model support the proposition that body odors provide a consistent 'odorprint' analogous to a fingerprint or DNA sample.”

“These findings indicate that biologically-based odorprints, like fingerprints, could be a reliable way to identify individuals,” shared the lead study author Jae Kwak, a chemist at Monell. “If this can be shown to be the case for humans, it opens the possibility that devices can be developed to detect individual odorprints in humans,” he added. Beauchamp is also experimenting with the idea of linking changes in individual odors to certain diseases, so that specially-designed devices that can already scan a person's unique smell could also provide useful information on their state related to pathological conditions, like cancer or viral diseases.