What causes rosacea? What the research shows

Nobody knows exactly what causes rosacea. The American Academy of Dermatology (AAD) says the cause is unclear, and the US National Institutes of Health (NIH) says scientists have a number of theories. What research does show is a set of factors that seem to play a part: inflammation, the immune system, tiny skin mites, genes and sun exposure. This guide explains each one in plain words. It cannot tell you whether you have rosacea. Only a doctor can confirm that, by looking at your skin and eyes and ruling out conditions that look the same.

For an overview of the condition, see what rosacea is.

Inflammation is the leading explanation

Inflammation is the body's response to injury or infection. It brings redness, heat and swelling. The AAD says many of the signs of rosacea, including flushing, acne-like breakouts and eye problems, may be due to inflammation.

This idea helps explain how rosacea changes over time. The AAD says inflammation could explain why rosacea begins with flushing that becomes lasting color, and why bumps develop later. As the inflammation increases, the signs increase too.

NIAMS, NIH's skin institute, agrees that inflammation drives key signs such as redness and rash. It adds that scientists do not yet fully understand why the inflammation happens.

The immune system and a protein called cathelicidin

The immune system protects the body from germs. Part of its job is to turn on inflammation when it senses a threat. The AAD says that in rosacea, the immune system may be set off by triggers like sunlight, heat or spicy food.

The AAD names one protein in particular. Cathelicidin normally helps protect the skin from infection. In rosacea, it may cause the color change (red on lighter skin, violet or brown on darker skin) and the swelling. How the body handles this protein may decide whether a person gets rosacea, the AAD says.

Researchers are also studying how the nerves and blood vessels of the face may play a part.

Tiny skin mites

Mites called Demodex live on nearly everyone's skin. They are too small to see without a strong microscope. The AAD says researchers often find these mites in greater numbers when someone has rosacea.

The theory is that the larger number of mites triggers an immune reaction, which leads to inflammation. This link is still being studied. The mites live on people without rosacea as well, so having them is normal. The guide to whether rosacea is autoimmune or contagious covers what this means for passing rosacea to other people.

A stomach infection called H. pylori

H. pylori is a type of bacteria that can infect the stomach. The AAD says this infection can stimulate the immune system and cause inflammation.

The research here is mixed. The AAD says some studies found that treating the infection calmed rosacea, and other studies found that treating it did not help. More research is needed. If you have stomach symptoms as well as rosacea, tell your doctor, who can decide whether testing makes sense.

Genes and family history

Rosacea runs in some families. MedlinePlus, from the US National Library of Medicine, says you may be more likely to have it if rosacea runs in your family. The AAD lists having a blood relative who has or had rosacea or severe acne as a risk factor.

The clearest numbers come from a study of twins published in JAMA Dermatology in 2015. Dermatologists examined 275 pairs of twins, most of them identical. Identical twins share all their genes, so comparing them with non-identical twins shows how much of a condition comes from genes. The study found that genes accounted for 46 percent of the rosacea score, and the environment accounted for the rest.

The same study found that higher rosacea scores went with older age and more lifetime sun exposure. They also went with smoking, alcohol, body weight, heart disease and a history of skin cancer. These are links. They do not prove that any one of them causes rosacea.

NIAMS says both genes and the environment likely play a role, and that more research is needed on genes.

Who is more likely to get rosacea

Anyone can get rosacea. A 2018 review in the British Journal of Dermatology pooled 32 studies covering more than 26 million people. It found rosacea in 5.46 percent of adults, most often between ages 45 and 60.

The AAD says women develop rosacea more often than men. NIAMS adds that when men get it, it tends to be more severe. The AAD says your chance of getting rosacea seems higher if one or more of these describe you:

• You are 30 or older
• You have fair skin, with blonde hair and blue eyes
• A blood relative has or had rosacea or severe acne
• You had many acne breakouts, or acne cysts and nodules
• You are going through menopause

The AAD adds that people who match none of these can still get rosacea. Dermatologists are diagnosing it more often in people of Asian, Latin American and African ancestry, and in people younger than 30. Children get it rarely.

Alcohol and rosacea

The AAD says research suggests drinking alcohol may raise the risk of getting rosacea. One study it describes followed 82,737 women for 14 years. Women who drank had a higher risk than women who did not, and the risk rose with the amount they drank. Women who drank white wine or hard liquor had a greater risk than the other women in the study. Two other studies, one of twins and one comparing 60,042 people with rosacea to 60,042 without, found the same link.

The AAD is clear on the limits. More studies are needed to know whether drinking causes rosacea. People who never drink can get it. Rosacea does not mean a person has a drinking problem.

Causes and triggers are two separate questions

A cause is why rosacea starts. A trigger is something that makes rosacea flare once you have it. The AAD lists sunlight, stress, heat, alcohol, spicy food, some skin and hair products, some makeup, wind and cold, some medicines and exercise as common triggers. Triggers differ from person to person.

Some things may be both. Sun exposure is linked with higher rosacea scores in the twin study, and the AAD calls the sun one of the most frequent causes of a flare. Alcohol may raise the risk of getting rosacea and also trigger flares.

Knowing your triggers is one of the few parts of rosacea you can control. The guide to rosacea triggers shows how to find yours with a simple diary.

How to read studies about rosacea causes

Most research on rosacea causes finds links. A link means two things appear together more often than expected. It does not show which one causes the other, or whether a third factor explains both.

The AAD's own pages show this care. On alcohol, it says studies found a link and that more studies are needed to know whether drinking causes rosacea. On a stomach infection called H. pylori, it says some studies found that treating the infection helped and others found it did not. On other diseases, it says the studies could not tell whether rosacea itself caused them. The 2015 twin study found that sun exposure, age, smoking and alcohol went with higher rosacea scores, and those are links too.

For a reader, the practical point is to treat any single claimed cause with care, especially when it comes with a product for sale. The factors with the strongest support are the ones the AAD lists as risk factors, and the triggers it lists as causes of flares.

What does not cause rosacea

The NHS states that rosacea is not caused by poor hygiene and that it is not contagious. The AAD advises against rubbing, scrubbing or massaging skin with rosacea, and recommends washing gently with the fingertips instead of a washcloth or sponge.

Why the cause matters for treatment

The AAD says there is no cure for rosacea at this time. Treatment aims at the signs each person has: lasting redness, bumps, visible blood vessels, eye symptoms or thickened skin. The guide to how rosacea is treated lists what a doctor may offer for each one.

Research is active. The AAD says scientific advances, many made by dermatologists, are giving a better understanding of what happens inside the body in rosacea. For now, the practical steps are a correct diagnosis from a doctor, a treatment plan, gentle skin care and avoiding your own triggers.