9 Common Causes of Rosacea

by Jerilyn Covert Health Writer

Imagine you have a motion detector in your backyard to alert you to intruders. But the sensitivity on the sensor is too high, so even harmless things (a squirrel, a fly) set it off. When you have rosacea, your immune system is like that alarm, says Richard Gallo, M.D., Ph.D., chair of dermatology at UC San Diego School of Medicine. A properly functioning immune system fights harmful substances. But in people with rosacea, it overreacts to certain stimuli, causing your face to develop redness or darkening, bumps, and/or visible blood vessels. But why does this happen in the first place? We’ve got answers.

skin mother child


Why do some people have more sensitive immune systems than others? Because of their genes. (Thanks, Mom and Dad.) That’s probably why people with a family history of rosacea are more likely to develop the skin disease. In fact, twin studies suggest that genetics may account for almost half the risk of developing rosacea—which of course also means your genetics are only half the story. You still need that “trigger” to set off the alarm. But before we get into triggers, let’s take a closer look at what happens during that immune response.

pimples rosacea


When that “motion detector” goes off, it signals your skin to produce proteins called cathelicidins, to help fight off the invader. Dr. Gallo’s research shows that people with rosacea not only have abnormally high levels of these molecules—but also that their cathelicidins aren’t normal. Instead, they resemble the kind that should be produced when you suffer a wound. This irregularity may cause the bumps, pimples, and flushing characteristic of the disease, Dr. Gallo’s research shows. “That’s not what you want healthy skin to do,” he says. “And that’s what happens in rosacea.”

close up rosacea

Mast Cells

People with rosacea also tend to have higher numbers of these white blood cells, which are part of the immune system. And recent research from UC San Diego shows that mast cells may play a role in activating cathelicidins. “Mast cells travel to the skin and sit there like little landmines,” explains Dr. Gallo. “They’re packed full of things to help defend the skin”—including cathelicidins. When they “blow,” those molecules are released. But what causes the chain reaction in the first place? Let’s talk triggers.

Demodex mites

Face Mites

One of the triggers could be Demodex mites, little critters that live in your face—in areas like the nose, cheeks, chin, and forehead where rosacea tends to show up. The bug’s numbers may increase with age, sun damage, or weakening of the immune system. Some rosacea responds well to anti-Demodex meds, suggesting a link. But don’t bother trying to scrub them off. Skin-care treatments like facials can actually increase your skin’s oil production, creating an ideal environment for the mites (and other microbes) to grow, says Dr. Gallo.



Still, the mites themselves may not be to blame so much as the bacteria that reside in their tiny intestines. Research shows that the bacterium, called Bacillus oleronius, triggers an immune reaction in rosacea patients even after it’s removed from the mite. It could be that when the mites die, the bacteria are released into the skin, triggering damage and inflammation, the researchers say. This could explain why rosacea can also respond well to antibacterial meds.

gut bacteria

Gut Bacteria

“There are a lot of connections between the skin and the gut,” says Dr. Gallo. And rosacea often occurs with GI symptoms. “It’s very likely that the gut immune system affects the skin, and the reverse is probably also true—that the skin affects the gut.” Some research links rosacea with an intestinal bug called Helicobacter pylori (H. pylori). In one study from Italy, almost half of rosacea patients were infected with H. pylori, versus only a quarter of people without rosacea—and 97% of patients successfully treated for the infection saw rosacea symptoms improve.

sun sensitive skin

UV Exposure

UV rays from the sun are the most common trigger for rosacea flares, reported by 81% of rosacea patients. Plus, exposure to UV radiation can damage the tissue around tiny blood vessels in the face, causing them to weaken and rupture, especially in those with lighter skin. “Individuals with lighter skin type are more susceptible to sun damage in general,” says Jessica Gandy Labadie, M.D., chief resident in the dermatology department at Northwestern University in Chicago. Plus, UV rays promote inflammation, which may also trigger the inflammatory cascade that leads to rosacea.

senior blushing


Rosacea tends to develop between ages 30 and 50—possibly the result of cumulative damage over time. “It may take years of very small unnoticeable damage before it becomes noticeable to the patient,” says Dr. Gallo. “Though we can’t say for sure if there’s undetectable rosacea in your late teens that only becomes visible in your late 30s.” The damage that builds may come from the same triggers that cause rosacea flares: spicy foods, heat, embarrassment—anything that makes you flush. Alternatively, hormonal changes that happen with age could be a trigger too, Dr. Gallo says.

woman worried about face


We don’t know why women develop rosacea more often than men do, but it may have to do with the immune system. “We know that the immune system in females operates differently than the immune system in males,” says Dr. Gallo. Women are also generally at higher risk for autoimmune disorders, suggesting they may have more-reactive immune systems to certain stimuli. Sex hormones may also contribute, though we don’t know exactly how, says Dr. Gallo. It could be that women’s hormones interact with their genes in a way that impacts the immune system.

Jerilyn Covert
Meet Our Writer
Jerilyn Covert

Jerilyn Covert is a writer, editor, and copy editor with 15 years of publishing experience. She’s written hundreds of articles for Men’s Health (where she was an editor for more than 10 years), Women’s Health, Runner’s World, ONE37pm, Whiskey Advocate, Silver Sneakers, and many more. She’s insatiably curious and loves interviewing people who know a lot more than she does. She shares their insights and advice so others can use them to improve their lives.