A much higher percentage of men with an unpleasant smell were found to have gonorrhea compared to other men, researchers from the Institute of Cytology and Genetics in Novosibirsk, Russia revealed in the Journal of Sexual Medicine. The authors explained that adult males with gonorrhea had a putrid smell, as far as many adult females were concerned.

As background information, the authors explained that animal research had demonstrated that rats and mice pick up on chemical signals to avoid sexual contact with infected potential mates. However, studies into body odor in humans have so far been limited to medical diagnostics. No studies had ever looked into smell modifications in humans, due to infection, and what impact that might have in choosing a sexual partner.

As STDs or STIs (sexually transmitted infections) have no clear visible external signs, the researchers wondered whether odor might be a sign that has been overlooked.

Mikhail Moshkin and team set out to determine whether odor unpleasantness in young adult males might be linked to infection with Neisseria gonorrhoeae (gonorrhea).

The researchers collected saliva and armpit samples from 16 healthy, 13 gonorrhea infected, and 5 other men who had recovered from gonorrhea after medical treatment. Healthy young female volunteers then assessed the sweat samples for odor (smell). With the saliva samples, the researchers measured for concentrations of testosterone, cortisol, immunoglobulin G (IgG), and immunoglobulin A (IgA). All the male participants were aged from 17 to 25 years and the female ones from 17 to 20.

Their aim was to determine whether the females could distinguish pleasant and unpleasant armpit sweat smells, and whether the differences might be linked to gonorrhea infection, no infection, or recent infection.

They found that:

  • The women described the odor from infected individuals as less pleasant compared to the healthy and recently recovered men. A very high proportion of samples from the infected men were rated as putrid (rotten, rancid).
  • There was a negative correlation between odor pleasantness and concentrations of nonspecific salivary IgA and IgC.

In an Abstract in the journal, the authors wrote:

“Perhaps, the immune-dependent reduction of the scent pleasantness in the acute phase of STI is part of an evolutionary mechanism ensuring, unconsciously, avoidance of a risky romantic partner.”

Written by Christian Nordqvist