Contrary to popular belief, new research suggests that drinking coffee might be a good prescription for avoiding the unsightly skin condition known as rosacea.
The finding is based on an analysis of rosacea risk and dietary habits among nearly 83 000 women who were enrolled in a national nurses' study between 1991 and 2005.
And it appears to challenge longstanding wisdom that those who struggle with rosacea should avoid both caffeine and hot drinks of any kind.
"In our study, we found that consuming caffeine from coffee may protect against the risk of developing rosacea," said study author Wen-Qing Li.
But the study did not prove that coffee causes rosacea risk to drop.
Li is an assistant professor of dermatology and epidemiology at Brown University in Providence, Rhode Island.
Rosacea is a common chronic inflammatory condition that affects the face in the form of flushing and blushing, and sometimes acne-like bumps. Former President Bill Clinton struggles with the disease, while Britain's Princess Diana had rosacea, too.
As to how much caffeine would be needed to reduce rosacea risk, Li said that coffee drinkers who consumed as little as 100mg of caffeine a day saw a 4 drop in rosacea risk.
And those who consumed four or more servings of coffee a day saw a "significant" drop in rosacea risk when compared with those who consumed less than one cup a month, the researchers found.
But calculating serving size can be tricky. The Mayo Clinic notes that an +/-240ml cup of coffee typically contains between 95mg and 165mg of caffeine, while the study team indicates that one would need to drink at least two servings of coffee a day to reach the 100mg threshold.
On the other hand, the Center for Science in the Public Interest points out that a single +/-600ml "venti" serving of Starbucks Blonde Roast coffee contains about 475mg of caffeine, while a single "large" +/-600ml serving of Dunkin' Donuts coffee with Turbo Shot contains about 400mg.
The other outstanding question is exactly why caffeine might reduce rosacea risk in the first place.
Li said the jury is still out, but he pointed to its potential impact on the strength of vascular contractions and the immune system. Risk reduction, he added, may also originate in caffeine's impact on levels of key hormones - such as adrenaline, noradrenaline and cortisol - or in the antioxidant agents it contains.
Still, Li stressed that the apparent association was only seen among coffee drinkers. No protection was linked to consuming other caffeinated substances, including tea, sodas or chocolate. Nor was any protective benefit linked to the consumption of decaffeinated coffee.
In fact, the analysis suggested that eating chocolate may actually increase rosacea risk, though Li noted that "the findings cannot preclude the potentially protective effect of caffeine consumed in other forms."
Among the larger pool of women in the study, about 5 000 had been diagnosed with rosacea at some point prior to 2005.
The research team then matched those rosacea diagnoses against detailed food and beverage reports taken every four years since 1991.
The study was published October 17 in the journal JAMA Dermatology.
Dr Robert Kirsner, chair of the department of dermatology and cutaneous surgery at the University of Miami Miller School of Medicine, suggested that while the findings were "intriguing," they should be interpreted with caution, given that "an association does not imply causality." He was not involved with the research.
Nevertheless, Kirsner said the findings may "help direct patients regarding dietary choices" and may ultimately lead to new therapies involving coffee.
Dr Mary Wu Chang, a clinical professor of dermatology and pediatrics with the University of Connecticut School of Medicine, agreed that the findings make sense, even if they are a "little bit surprising."
But Chang, who had no role in the study, noted that the degree of benefit observed was "not that much. So I'm not sure what to conclude or recommend, based on this.