Demand for red lipstick among waitresses might increase following a study that revealed red lipstick boosted tips from male customers.

According to medicaldaily.com, Nicolas Guéguen and Céline Jacob of the Université de Bretagne-Sud found that male patrons gave tips more frequently to waitresses wearing red lipstick than to other waitresses, and that they gave more when they tipped.

The researchers say they asked seven waitresses to wear red, pink, brown or no lipstick while serving 447 customers in three restaurants in the town of Vannes. In France, tipping is unusual because a 12% service charge is included in the price of the menu item.

Interestingly, Guéguen and Jacob say that a waitress's lipstick or lack of it appeared to make no difference in how female patrons tipped.

The study, which appears in the International Journal of Hospitality Management, claims that previous research showed men gave more tips to female waitresses wearing full facial makeup, but until now, no study has looked at the effect of lip colour alone.

As for the appeal of red lipstick, the team suggests red lips could be associated with estrogen levels, sexual arousal and health.

"Such positive perceptions of the women could perhaps explain why men gave more tips to the waitresses wearing red lipstick in this experiment," wrote the French team.