Prince Harry sports one, Justin Trudeau has recently grown one, and Brian Blessed’s is almost its own being. But are beards attractive? As the old adage goes: “Depends on the man, depends on the beard.”

Now researchers have found there might be another factor: whether a potential partner fears there might be something living in it.

Scientists say women who are more repulsed by the idea of lice, fleas, ticks and other such ectoparasites, are less likely to find beards attractive, possibly because such pests might carry diseases.

“This is likely to be the case for the majority of our evolutionary past,” said Anthony Lee, of the University of Stirling, a co-author of the study. “In modern times, with increased grooming and overall better hygiene, this link between hairiness and carrying ectoparasites may no longer exist, but the evolved tendency may still persist.”

Whether facial hair boosts men’s pulling power or is a turnoff has long been a matter of contention, but previous research from the same team found women rate bearded men as a better bet for a long-term relationship.

Writing in the journal Royal Society Open Science, researchers from the University of Queensland, and the University of Stirling, report how they asked 919 predominantly heterosexual women to rate the attractiveness of three male faces for both potential short and long-term relationships.

Each face was shown with and without a beard, and with five levels of “masculinity” – while beardedness is seen as masculine, the trait includes a range of other features such as a thick jawline, a prominent brow, and deeply set narrow eyes.

The women also completed a set of questionnaires which measured attitudes including their revulsion in response to parasites that live on the body, and their desire to become pregnant.

In general, women deemed masculine-style faces more attractive than feminised ones. The same trend was seen for both short and long-term relationships and whether bearded or not, although differences in attractiveness relating to masculinity were less pronounced for bearded men – possibly, the team say, because the beard can hide some “unattractive” features.

For each level of masculinity, bearded men were deemed more attractive than clean shaven men, a result found for both short-term and, to a slightly greater degree, long-term relationships.

But not everyone was drawn to a hairy face. Among other results, the team found that women who had higher levels of disgust for ectoparasites found beards less attractive, although the reverse was true for those concerned about picking up harmful bacteria or viruses.

While the latter link was weak, the team write: “This could be interpreted as evidence that facial hair is preferred as a marker of health among women with high pathogen concerns, or that facial hair masks areas of the face that would communicate ill health.”

Whether participants were aware of a small study published last year that suggested men’s beards might harbour more germs than dog fur was unclear.

The study has limitations: all of the male faces were of northern European ethnicity, and most of the women were white and lived in the US. It is also not clear whether the results would hold for gay men, or women of other sexual orientations.

Lee said that despite the findings men should stick with what they were most comfortable with. “I wouldn’t base the decision to grow a beard on the results of a single study,” he said.

Christopher Watkins, from Abertay University, Dundee, an expert in social judgments of faces, who was not involved in the study, suggested further studies might explore whether men chose to cultivate facial hair if it were deemed sexier.

The authors of the study reveal that previous research into London fashions suggested facial hair was more common when there were more men than women available in the marriage market.

“The research advances work on individual differences in women’s attractiveness judgments, in this case, by focusing on facial cues that men can easily change – beards – in addition to how ‘masculine’ his face looks,” said Watkins. “Findings such as this might raise interesting questions in future about the uptake and nature of male grooming practices for example if different men from different cultures or regions are responsive to the high or low ‘value’ of a beard in making a good first impression.”