A quick spritz with the so-called "love hormone" oxytocin seems to keep men who are already in committed relationships from straying, a new study finds.

Oxytocin is made naturally in the body and has long been associated with feelings of love and trust.

The hormone, which is produced in the brain's hypothalamus, plays an important role in triggering childbirth and promoting breast-feeding. It is also known to promote bonds between parents and children and in couples.

In this study, researchers used nasal spray to give oxytocin or a placebo to a group of 86 heterosexual men with an average age of about 25.

Among men in committed relationships, those who received oxytocin kept a greater distance when approaching or being approached by an unknown female researcher whom they considered attractive, compared to those who received the placebo.

Oxytocin had no effect on single men and did not affect the distance the participants kept between themselves and other men, according to the study, which appears in the Nov. 14 issue of The Journal of Neuroscience.

"Because oxytocin is known to increase trust in people, we expected men under the influence of the hormone to allow the female experimenter to come even closer, but the direct opposite happened," study leader Rene Hurlemann, of the University of Bonn, in Germany, said in a journal news release.

The findings suggest that oxytocin may help men remain faithful to their female partners.

"Previous animal research in prairie voles identified oxytocin was a major key for monogamous fidelity in animals," Hurlemann said. "Here, we provide the first evidence that oxytocin may have a similar role for humans."