Is it just Toxoplasma gondii, or are you looking incredible tonight? If that’s not a sentence you thought you’d read, neither did we – but according to a new study published in the journal Brain, Cognition and Mental Health, the parasite responsible for affecting the host’s brain and potentially causing neurological conditions may actually make the host more attractive. Welcome to 2022’s worst new beauty trend. 

Toxoplasma gondii is a parasite spread by cats that can infect humans, causing a condition called toxoplasmosis. It presents with minimal-to-no symptoms unless the host is immunocompromised, in which case toxoplasmosis can be deadly.

Once established in the host human, it can then be spread through sexual contact. This sexual transmission poses a challenge to the parasite – have too much of an effect on the host, and they are unlikely to find a mate and spread it further. 

How Toxoplasma gondii manipulates the brain is fairly well characterized, but whether it changes phenotype (what we see when we look at another person) is poorly understood. Researchers hypothesized that it could change the characteristics of the host to increase the chance of sexual reproduction, and put it to the test in a new study. 

Taking a sample of 35 infected people and 178 non-infected people, a separate group of "raters" were asked to rate each participant on their perceived attractiveness, while metrics that could play a role in attractiveness were taken from each. These included body mass index, face symmetry, minor ailments, and more.

When all the results were tallied, a significant difference between the two groups emerged. Infected people were rated as healthier and more attractive across the board, with infected men having more symmetrical faces and infected women also having more symmetry, more sexual partners, lower BMI, and higher perceived attractiveness.

These results are in line with previous research in rats, suggesting that the parasite may either directly change the facial and bodily characteristics of a host to increase their chance of mating, or the by-products of infection just happen to be beneficial (aside from the health risks). 

Some studies have identified testosterone increases in males infected with Toxoplasma gondii, which could account for the changes in facial structure seen in men. Alternatively, healthier people may be able to afford the physiological costs of having a parasite, skewing the samples of people infected. Regardless, much more work needs to be done to understand just what is happening at a cellular level for parasites to change human phenotypes so drastically. 

The authors believe the work could be extremely important in understanding how parasites and human hosts interact.  

“Taken together, these results lay the foundation for future research on the manipulation of the human host by sexually transmitted pathogens and parasites,” write the authors.