Study suggests attractive people have stronger immune systems

A team of researchers at Texas Christian University has found that people perceived as more attractive by others tend to have a stronger immune system. In their study, published in Proceedings of the Royal Society B, the group asked volunteers to rate the level of attractiveness of people in pictures.

In most human societies, some people are deemed more or less attractive than others. In this new effort, the researchers wondered why this is the case. They theorized that it likely has evolutionary roots. And because most evolutionary traits can be tied to reproductive success, they further theorized that people who seem attractive to others may be better reproductive partners because they are healthier than average. To find out if this might be the case, they first recruited 159 male and female volunteers and photographed each without any makeup and with a neutral facial expression. They then performed blood tests on the participants to provide the researchers with an indication of overall health—in this case, the strength of their immune systems, by measuring white blood cell levels that combat diseases. The researchers then asked 492 other male and female volunteers to rate people of the opposite gender in the photographs on their attractiveness.

The researchers found that those judging the attractiveness of others based on nothing but a single photograph found those people with stronger immune systems to be more attractive, despite not knowing anything about their immune systems—they were somehow able to see it in the faces they were looking at.

The researchers also found that the female volunteers, on average, saw those males with higher levels of NK cells in their plasma as more attractive. Such cells target and kill bacteria. Interestingly, the reverse was not true for males looking at females—they found those with lower NK levels to be more attractive. The researchers suggest this is because women with lower NK levels tend to have higher estrogen levels.

Notably, the volunteers were asked to judge the attractiveness of the people in the photographs, not to judge how pretty or handsome they were. A person can be seen as attractive to others even if not perceived as better-than-average-looking.