Consider the rank odor of the old man perspiring beside you on the bus, the fresh smell of cut grass, the foulness of the passing garbage truck, or the appetizing aroma wafting out of the local bakery. Odors constantly surround us in countless forms, both positive and negative, but few of us stop to think about them. Scientists and laymen alike have long considered humans to be “microsmatic animals,” meaning that for us, the olfactory sense plays a minor role compared to the other senses. However, an increasing number of studies have begun to paint a different picture, one that suggests that olfactory information plays a very significant role in our everyday decisions. This article reviews recent insights into how the human brain processes body odors and the implications this may have for both lifestyle and use of perfumes and personal hygiene products.
Need for a Reality Check?
Body odors carry informational cues of great importance for the individual across a wide variety of animal species. For a long time, the thought that humans could be counted among these species was dismissed outright. However, it is now known that each of us has a unique odor that carries information related to our genetic makeup and also about personal environmental variables such as diet and hygiene. And, much like our fellow animals, humans are able to extract biological and social cues from conspecific body odors (i.e. odors from our own species) that provide information and direct our behavior. For example, studies have demonstrated that human body odor conveys information that allows us to identify individuals, directs us toward a partner with an advantageous genetic makeup, and informs us of the health status of others.1,2,3
Body Odors and the Brain
The percept, or mental impression, of a body odor commonly includes an emotional character that evokes a strong valence of liking or disliking. For example, the body odor from a lover may be a very pleasant percept, whereas the same percept from the person sitting next to you on the bus may be highly negative. When we hear the two words “body odor,” most of us think about an unpleasant percept related to heavy perspiration. This odor is consciously perceived and reflects a response to a small subset of the numerous chemicals (about 120) that comprise an individual’s body odor. In contrast, we typically are not consciously aware of perceiving the chemicals within our or others’ body odor that serve as social signals.