Your genes and immune system play a role, but it's also important to know and manage your triggers.

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A psoriasis flare-up can be uncomfortable, both physically and emotionally—and all the more frustrating when it strikes at an inopportune time.

While the cause of psoriasis isn't exactly clear, there's some evidence that your immune system and the genes you inherit play a role, says National Psoriasis Foundation (NPF). But those factors don't tell the whole story.

Understanding what's triggering your psoriasis flare-ups can help you gain better control, says the American Academy of Dermatology (AAD).

We asked dermatologists to unpack the complexities of how those itchy, painful patches come to be. Here's what to know about the causes and triggers of psoriasis.

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Credit: Getty Images

What causes psoriasis—and what role do your genes and immune system play?

Up to 7.5 million US adults have psoriasis, a non-contagious disease characterized by scales or plaques on the skin, says NPF. It's sometimes described as an immune-mediated disease, meaning the immune system's response is excessive.

"The body's immune system recognizes a normal protein in the skin and thinks its abnormal and doesn't belong there," Joel Gelfand, MD, professor of dermatology and director of the Psoriasis and Phototherapy Treatment Center at the University of Pennsylvania Perelman School of Medicine tells Health. "If the immune system thinks something is wrong in the skin, it reacts by inflaming it, causing the skin cells to proliferate rapidly, trying to flake it off."

Dr. Gelfand explains that a normal skin cell takes around 30 days to flake off, but in someone with psoriasis, the process occurs in just a few days, leading to build-up and red patches on the skin that can itch, crack, and bleed.

According to NPF, there are five types of the disease, with plaque psoriasis being the most common. Though it can occur anywhere on the body, psoriasis typically appears on the scalp, knees, elbows, and lower back.

Roughly one third of people diagnosed with psoriasis will also develop psoriatic arthritis, an inflammatory condition that causes stiffness and swelling in the joints, says the Arthritis Foundation. And while science hasn't been able to pinpoint the underlying cause of psoriasis, there's a genetic link.

"Family history plays a role, and it does sometimes occur in multiple members of the same family," Jeffrey M. Cohen, MD, assistant professor of dermatology at the Yale School of Medicine, tells Health. "And we don't believe that's just coincidence. We do believe that there is some underlying genetic susceptibility."

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Credit: DermNet NZ

Knowing your risk for psoriasis

For those genetically predisposed to the disease, Dr. Cohen says that there are certain risk factors that can increase the odds of developing it.

"Cigarette smoking, alcohol use, certain medications are environmental factors that might bring out psoriasis in someone who's genetically susceptible," says Dr. Cohen. And while genes or environmental factors can play a role in causing some people to develop the disease, the "exact mechanism" of why people get it remains a mystery, he adds.

As sufferers know, flare-ups can come and go with little-to-no warning, but any number of possible triggers are thought to contribute to bouts with the disease. "When flares of psoriasis occur, the first thing that needs to be done is to identify the cause and rule out an infection as the triggering event," says Dr. Gelfand.

What causes psoriasis flare-ups?

Unsurprisingly, experts say some of the same triggers that can lead to the initial onset of psoriasis are also thought to be responsible for subsequent flare-ups and include stress, skin damage, alcohol, cigarette smoking, infection, weather, and certain medications.

Bad and good stress

You've heard it before: Stress can be bad for you. But it bears repeating. According to the National Institute of Mental Health, long-term stress not only affects your mental health, but it can have a serious impact on your physical health, too, contributing to everything from heart disease to diabetes.

It's also the number one cause of psoriasis flare-ups, Howard Feinberg, DO, professor of rheumatology at Touro University California, tells Health.

"That can be any type of stress; it can be physical stress because somebody isn't sleeping well at night, or isn't eating well, or got sick from something else, and that caused a flare-up of their disease. It can also be emotional stress; somebody who's going through depression with the COVID pandemic," he says.

And according to Dr. Feinberg, it's not just the obvious "bad" stress that can lead to flares. "Good" stress can have the same effect.

"I've had patients who told me that getting married is what caused their disease to flare, and it wasn't really the marriage that did it, it's just the stress of planning a wedding, and all the things that are involved with that. Even though it's a happy event and a happy occasion, it's very stressful."

Injuries or damage to your skin

Though a minor cut or scrape may not seem like a big deal, it can potentially lead to a flare-up according to Dr. Feinberg, who says that skin lesions are a common source of local flares.

"Almost anything that causes damage to an area of skin can cause psoriasis to come out when we're dealing with an overall flare-up of the disease," he explains. "It can be any type; a small cut or injury."

Getting a sunburn can also be the cause of flares. As AAD points out, "even a mild sunburn can worsen existing psoriasis and cause new psoriasis to form."

Heavy drinking

A glass of wine or beer isn't likely to bring on an acute bout of psoriasis, but in people susceptible to the disease, heavy drinking can. The Centers for Disease Control and Prevention (CDC) defines "heavy drinking" as more than 15 drinks per week for men, and eight for women.

And while the relationship isn't well-understood, Dr. Feinberg says that there's an association between the two. "We found that patients with psoriasis, for some reason, have a higher alcohol consumption, and there's a relationship between that and psoriasis," he says. However, the exact connection remains the subject of ongoing research, according to a 2019 review.

Smoking

Cigarette smokers with a genetic predisposition for psoriasis are at greater risk of developing the disease, but the jury is still out on whether or not it can cause flare-ups.

"Smoking doesn't really cause psoriasis to flare up," says Dr. Cohen. "If you smoke, you're more likely to have psoriasis. And if you stop smoking, your psoriasis may become less severe."

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Credit: DermNet NZ

Illness or infection

NPF says anything that affects the immune system can trigger psoriasis. Flares can occur following a variety of illnesses including ear infections, bronchitis, tonsillitis, and respiratory infections.

Strep throat has also been associated with the disease, and it can be the catalyst in initial onset of psoriasis, especially in children, NPF points out.

Dr. Feinberg says that, overall, being sick is generally hard on the body. "It stresses the entire system and can allow both psoriasis and psoriatic arthritis to get worse," he explains. "And it doesn't matter what type of illness; a cold or flu can certainly cause a flare-up."

Some initial research suggests that psoriasis sufferers may be more prone to contracting COVID-19. "Because this is a new infection, we don't have a lot of that information available, but there is some information that people with psoriatic arthritis could be more prone to getting the infection," Dr. Feinberg says, "and maybe have a worse course with the infection."

Though it's still too early to know for sure, COVID-19 also appears to affect flare-ups, says Dr. Gelfand. "For people with psoriasis, common causes of flares are stress, alcohol, smoking, and infection, particularly strep infections. There have also been many reports of COVID-19 causing severe flares of psoriasis. It is critically important for people living with psoriasis to get vaccinated."

Changes in the weather

The fall and winter months can be tough for some people with psoriasis. Lack of sunlight, along with dry, cold, weather often robs the skin of much-needed moisture, leading to a potential psoriasis flare-up, says AAD. Surprisingly, warm weather can, too, if it means spending a lot of time inside with the air conditioning running, explains AAD.

Fluctuations in temperature, humidity, and barometric pressure can prompt flares in people afflicted with psoriatic arthritis, causing painful inflammation and stiffness in their joints, according to Dr. Feinberg. "I get better weather reports than any weather station could provide because of my arthritis patients," he says. "So, the old 'I feel it in my joints, we're going to have a storm coming,' is absolutely true."

Taking certain medications

For some people, certain medications can induce a psoriasis flare-up.

Beta blockers, typically prescribed for high blood pressure and heart conditions, are among some of the most common, says Dr. Cohen. Systemic steroids are another. "If you have psoriasis, and you take prednisone, when you come off the prednisone, your psoriasis often flares up," Dr. Cohen explains.

Though topical steroids are commonly used to help treat psoriasis, he says, oral or intravenous steroids can exacerbate it. "Those, when you come off, there's a concern that they can cause a really bad psoriasis flare."

Because of that, Dr. Cohen says that patients are advised to avoid them whenever possible.

Other medications that can trigger flare-ups include hydroxychloroquine, a malaria drug frequently used in treating rheumatoid arthritis and lupus, and indomethacin, a medicine prescribed for arthritis.

Less common medications like lithium, used for treating certain psychiatric disorders, can also affect the disease, according to Dr. Feinberg, who says that, in general, psoriasis triggers are largely dependent on the individual.

"It isn't universal. It's not something that would apply to everybody with that problem," he says. "So, we want people to be conscious of their own body, and if they are taking something over-the-counter, or they're eating certain types of food, and they notice that it seems to affect them, they want to avoid those things."

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