Single People Smell Different. Here's Why

Do you ever feel so lonely you suspect you might physically reek of despair? Does singleness literally ooze out of your pores, congealing in sweat droplets that stick to your skin? When strangers catch a whiff of your scent as you stand close in the elevator, is it your solitude they smell? No, but it might be your testosterone level, immunity to pathogens, and fertility status. Body odor, like breath, is omnipresent, and it contains a wealth of information about your health, fitness, diet, menstruation, genetic makeup, and possibly even if you're single.

Multiple experiments indicate we can gauge a potential partner's sexual desirability simply from the smell of their sweat (via BBC). While the impact of body odor on attraction is not absolute, our body odor does convey important information about our genetic immunity to certain pathogens, which could have helped our ancestors select a desirable mate with compatible genes in order to produce viable, healthy offspring.

Our body odor reveals the state of our current endocrinology (or hormone levels), including information about immunity to certain pathogens, our overall health, and our hormone levels. Our hormone levels are influenced by our lifestyle (as noted by Sari van Anders and Neil Watson in their 2006 study published in Human Behavior), and our lifestyle is influenced by our relationship status (via HCP Live). At least, that's what researchers found in a 2019 study at Macquarie University.

The Experiment

A study conducted by Macquarie University in 2019 used the "t-shirt experiment" model to test perceptions of attractiveness discerned through body odor varies between single and partnered men. The conclusion? Single men smell different. Well, to be precise, single men just smell more.

Eighty-two heterosexual women, 42 of them single and 40 in partnered relationships, participated in an experiment at Macquarie University. Ninety-one heterosexual men were given white cotton t-shirts and instructed to wear them until the shirt was thoroughly soaked with sweat so as to preserve their body odor. The researchers presented each of the 82 women with six "samples" from six different men — three of them partnered and three of them single — and asked the women to rate each man on five different qualities ("Sexy," "Familiarity," "Like," "Similarity," and "Strong, via Mahmut and Stevenson in Frontiers in Psychology, 2019). Here's what they found: single men's body odor smells ... "strong"?

Why might this be? Researchers have a theory: It's either their testosterone levels, their poorer health, or their hygiene. In earlier studies, higher testosterone has been found to be correlated with strong BO (as noted by Mahmut and Stevenson), and there is evidence single men may have higher testosterone levels. This is possibly due to the endocrine effects men in relationships experience as a result of intimate-partner bond maintenance (via a 2010 study by van Anders and Goldey in Human Behavior).

The Explanation

Our hormone levels (which include testosterone) are also a product of our health, diet, and other lifestyle factors, all of which are impacted by relationship status (via HCP Live). The authors of the Macquarie study theorized this testosterone could be the factor in the difference women can detect.

Alternatively, the researchers theorized single men's BO might smell more pungent "due to poorer health and hygiene" (Mahmut and Stevenson, 2019). The team pointed to extant factors affecting BO such as single men's weaker health (citing a 1990 study by Hu and Goldman in Demography) and single men's decreased tendency to seek medical care (citing a 1996 study by Norcross, Ramirez, and Palinkas in Journal of Family Practice) compared to men in relationships.

Wellness-enhancing activities, stress, perceived safety, activity, and familial bonds all trigger certain chemical processes, resulting in altered hormone levels (via BBC). If we can sense these chemicals, such as testosterone levels, we can probably infer that the situations sparking or inhibiting the production of these chemicals are ones our bodies can infer as well. Such is the case with singleness.