(NaturalNews) Men carrying certain sexually transmitted infections may actually smell worse to women than men without such infections, according to a study conducted by researchers from the Institute of Cytology and Genetics in Novosibirsk, Russia and published in the Journal of Sexual Medicine.
"Our research revealed that infectious disease reduces odor attractiveness in humans," lead researcher Mikhail Moshkin said. "We can conclude that unpleasant body odor of infected persons can reduce the probability of a dangerous partnership,"
Moshkin and his fellow researchers had previously observed that female rats and mice appeared to be less attracted to -- or even actively repelled by -- the smell of males who had been infected with viruses or parasites. They wanted to find out if human females have any similar ability to detect infection with their noses.
To test the hypothesis, the researchers selected 34 male participants between the ages of 17 and 25. Thirteen of the participants were currently infected with gonorrhea, five had previously been diagnosed with the infection but had since been treated, and sixteen did not have any sexually transmitted infection.
Researchers collected spit samples from all the male participants, and also had them wear t-shirts with cotton pads in the armpits. After an hour of sweating, the men placed their t-shirts in a bag and the cotton pads were placed in glass vials.
Eighteen female students from Kemerovo State University, all between the ages of 17 and 20, were asked to smell the sweat samples and rate the smell on a scale of one (least pleasant) to 10. They were also asked to choose the word from a list that best described the odor; options included floral, fruity, minty, putrid, vegetable and woody.
Infected men smell more "putrid"
The women rated the sweat of the healthy men nearly twice as pleasant as that of the infected men. They judged nearly half of the infected men's samples as foul-smelling. In contrast, only one-third of the overall samples were rated as foul-smelling.
Similarly, while 26 percent of the healthy men's samples were described as "floral," only 10 percent of the samples from the infected men were described with that adjective. A full 40 percent of the infected men's samples were described as "putrid," compared with just 30 percent of the samples from the healthy men.
The researchers concluded that women have a definite ability to discern a difference in smell between infected and healthy men, perhaps as "part of an evolutionary mechanism ensuring, unconsciously, avoidance of a risky romantic partner."
While the mechanism by which women seem to be able to "smell" infection remains unknown, the researchers believe that the men's immune system may play a key role. They found that the higher the concentration of antibodies in a man's saliva, the less pleasant the smell of his sweat to women. This finding "call[s] attention to the crucial role of the immune system in the modulation of odor attractiveness resulting from an infection," the researchers wrote.
The researchers noted that while the results are certainly suggestive of a significant smell difference, men with sexually transmitted infections can mask their scent effectively with deodorant.
Whether women with sexually transmitted infections or men with infections other than gonorrhea smell noticeably different from healthy women and men remains unknown.