There is a growing body of research that claims sexual attraction between two people is based on their immune system. Before, dozens of theories tried to explain that sexual attraction happens after assessing a mate based on their physical attributes. These include the width of women's hips for childbearing or the height and muscles of men that signal an ability to provide and protect.

However, these theories are now obsolete and may fail to explain nor take into account same-sex attraction. It could be that characteristics that the eyes fail to perceive might give better clues to human attraction.

This could involve the sense of smell of humans that is a unique sense shared by other mammals, as well as reptiles and insects.

 People's Immune System May Be Key to Sexual Attraction, Studies Claim
(Photo: Pixabay)
People's Immune System May Be Key to Sexual Attraction, Studies Claim

An Attractive Immune System

The olfactory system is responsible for the sense of smell and has access to the deeper parts of the brain, unlike other senses. It serves several functions, such as communication, protection, and mate selection. Given the strong link between smell and the limbic system, it is no wonder smells can evoke feelings in humans, which bypasses consciousness and is likely to influence people.

A 2001 study titled "The Sweet Smell of the Immune System," published in Nature, suggests that the way a person wants to smell reflects their mean histocompatibility complex (MHC), or also commonly referred to as human leukocyte antigens (HLA) in humans. It is part of the genome that plays an important role in sexual attraction and the immune system.

That means the perfume industry should not put their hopes too high to concoct a universal scent that everyone loves because each person has a unique taste in scents. Preferred perfumes of each person could amplify certain aspects of it to alert compatible mates and give them a general impression of health.

Researchers tested responses from men and women to see how much they would prefer one scent to another. They saw a significant correlation between the person's MHC to what they would like to smell. But they found no significant trends in the smells they preferred for potential partners.

According to NY Daily News, previous studies reveal that the more a person's perspiration smells different from their potential mate, the more pleasant they are likely to find them attractive. Theories suggest that this phenomenon came about, so people would not accidentally marry their relatives or anyone with similar genes.

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Human Attraction Is Multifaceted and Complex

According to an article in Medium, the immune system argument is also limited as it mainly pertains to reproduction, excluding same-sex attraction. If only the HLA diversity is used to explain sexual attraction, it would not explain homosexual relationships.

On the other hand, the theory of attraction by smell could explain the attraction between similar sexual orientations. For instance, the study titled "Preference for Human Body Odors Is Influenced by Gender and Sexual Orientation," published in SAGE journals, shows that gay men have a unique preference for smell in both heterosexual women and other gay men over heterosexual men.

The study claims that it is possible that people are attracted to dissimilar HLA regardless of sexual orientation, which weakens the reproduction argument. However, limited studies on same-sex relationships leave a gap in the current understanding of sexual attraction. 

Nevertheless, as Medium reports, this proves that human attraction is a multifaceted and complex phenomenon that pulls humans to desire others based on a myriad of factors. Studies also show that humans, like other animals, can sense HLA or MHC that are different from their own and show more preference to those with the most differences.

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