Studies add clarity to link between rosacea and Demodex, coffee

LAHAINA, HAWAII – Recent data on the roles of caffeinated coffee and two types of Demodex species play in rosacea were discussed by Linda Stein Gold, MD, at the Hawaii Dermatology Seminar provided by Global Academy for Medical Education/Skin Disease Education Foundation.

Dr. Linda Stein Gold

When considering rosacea triggers, the role of coffee has been difficult to determine, according to Dr. Stein Gold, director of dermatology research at the Henry Ford Health System in Detroit.

“We know that caffeine can vasoconstrict, it also has anti-inflammatory properties so ... that might help rosacea,” while the heat from a hot cup of coffee may cause vasodilation “and make rosacea worse,” she noted.

But a recent study of data from the Nurses’ Health Study II that evaluated intake of coffee, tea, soda, and chocolate every 4 years in over 82,000 women shed some light on the role coffee may play (JAMA Dermatol. 2018 Dec 1;154[12]:1394-1400). There were almost 5,000 cases of physician-diagnosed rosacea in the cohort. When the investigators looked at caffeinated coffee consumption, “the more caffeine and the more coffee they drank each day, the more likely it was for them not to have rosacea,” she said.

Those who consumed four or more servings of caffeinated coffee a day had a significantly lower risk of rosacea, compared with those who consumed one or fewer servings per month (hazard ratio, 0.77; 95% confidence interval, 0.69-0.87; P less than .001).

But there was no significant association with decaffeinated coffee or with edibles that contained caffeine such as tea, soda, and chocolate, “so something about caffeinated coffee seems to be protective for the development of rosacea,” Dr. Stein Gold said.

Demodex mites

A few years ago, “we really didn’t think much of Demodex, but now we know Demodex tends to be a key player” in people with rosacea, Dr. Stein Gold said.

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Demodex mite

In adults, the colonization rate of Demodex ranges from 70% to 100%, but the skin of people with rosacea have a particularly high density of Demodex: About 35%-50% of patients with rosacea have an increased Demodex load above 5 mites per cm², as measured with a standard skin surface biopsy, she noted. The density of Demodex in the skin of patients with rosacea has been measured at sixfold higher, compared with age-matched controls.

There also are two different Demodex species: Demodex folliculorum, which are longer, and Demodex brevis, which are short, and there is evidence that each “may cause an individual reaction,” Dr. Stein Gold said.

She referred to a study that found a difference in the Demodex population in patients with highly inflammatory disease with a high level of Demodex, mild rosacea patients who did not have a lot of Demodex, and people with no rosacea (Dermatol Reports. 2019 Jan 23;11[1]:7675).

“Those people who had really severe, inflammatory rosacea had Demodex folliculorum,” and the patients with the more mild disease or those with clear skin had Demodex brevis, she said, so “different species of Demodex might cause a different inflammatory reaction within individual rosacea patients.”

Dr. Stein Gold reported that she has served as a consultant, investigator, or speaker for Galderma, Dermira, Foamix Pharmaceuticals, Valeant (now Bausch Health), Allergan, Actavis, and Roche.

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