Let's Talk About the Causes of Psoriasis
If you have this itchy skin condition, you might be scratching your head trying to figure out how you got it. Here, the top reasons you’re seeing those telltale red spots and scales.
Psoriasis can be a pain: It's often itchy and stings like whoa. It might also make you feel self-conscious because psoriasis lesions can be prominent on your arms, legs, and face. If you have it, it might help to know that you're not alone: More than 8 million Americans are in the same boat. Still, you're probably wondering, why me? Good question. Understanding the causes and triggers can help you keep this chronic condition under control—and, hopefully, stay in the clear.
Our Pro Panel
For the most up-to-date info on the causes of psoriasis, we reached out to top skin doctors across the country.
April W. Armstrong, M.D.
Professor of Dermatology, Associate Dean for Clinical Research and Psoriasis Program Director
Keck School of Medicine and Department of Dermatology at the University of Southern California (USC)
Los Angeles, CA
Mark Lebwohl, M.D.
Chairman of the Kimberly and Eric J. Waldman Department of Dermatology
Icahn School of Medicine at Mt. Sinai
New York, NY
Lawrence Eichenfield, M.D.
Chief of Pediatric and Adolescent Dermatology, Professor of Dermatology and Pediatrics
Rady Children's Hospital and University of California, San Diego School of Medicine
San Diego, CA
No. You can’t catch psoriasis from someone else or give it to someone. Psoriasis is caused by an overactive immune system and possibly genetics, combined with an environmental trigger. It is not caused by skin-to-skin contact.
Yes. Foods and beverages known to increase inflammation and potentially worsen psoriasis are alcohol, processed sugars, dairy, gluten, and nightshade produce. On the other hand, a Mediterranean diet (fish, leafy greens, olive oil, whole grains) may ease psoriasis symptoms.
Genetics appears to play a major role in developing psoriasis so, yes, you’re more likely to get this skin condition than someone whose mother doesn’t have it. Your chances of inheriting psoriasis from one parent is 10%, so you’re not destined to get it. If both your mom and dad have it, your chances go up to 50%. Does your risk increase if a second-degree family has it (grandparents, aunts, uncles)? It appears to. In one study found of 380 people with plaque psoriasis, 16% had a secondary relative with the disease, and 5% had a third-degree relative (cousins, great-grandparents, etc.).
Can’t happen. The two are unrelated and it’s unlikely you would have both skin conditions. Eczema is also thought to be caused by an overactive immune system and genes, but different ones. Many people with eczema have a gene mutation that makes them lack fillagrin, a protein that keeps your barrier strong and intact. Without enough of it, irritants, allergens, and bacteria get into the skin, causing an inflammatory response: eczema. Psoriasis is caused by an overactive immune system that causes a buildup of skin cells on skin’s surface, which turn into red, painful, and itchy patches.
What’s Psoriasis, Again? Let’s Recap
Psoriasis is an inflammatory skin condition marked by red, scaly patches of skin that can appear as small bumps or thick, raised lesions. These can crop up anywhere on the body, but the most typical spots are knees and other parts of the legs, elbows, torso, and face.
While psoriasis doesn’t discriminate by age and can appear at any time, it usually makes its debut sometime between 15 and 35 years old. And unlike some diseases that favor one gender over another, psoriasis is an equal opportunist: It strikes women and men in the same numbers.
There are seven different types of psoriasis. When you think about the condition, you’re probably picturing plaque psoriasis, the most common type. It affects 80% of those with psoriasis. Its lesions, called plaques, are red, scaly, and clearly demarcated, with peaks that can look silvery (on lighter skin) or purple (on darker skin). The other, less common types of psoriasis are:
Guttate: This is the second most common form, which shows up as small red tear-shaped bumps on upper arms, trunk, thighs, and scalp.
Inverse: This causes bright red, shiny patches in folds of skin such as your groin, underarms, under breasts, and around genitals that tends to get worse from sweating and friction.
Pustular: As the name implies, this type of psoriasis appears as pus-filled bumps, often on hands and feet. If it covers most of your body and comes with flu-like symptoms and an increased heart rate, it can be dangerous and needs medical attention, stat.
Erythrodermic: This condition presents as widespread, red skin that looks like a burn. It’s the least common of all the psoriasis types.
Psoriatic arthritis: This version of the disease occurs when you have both psoriasis and arthritis—achy, swollen joints and inflamed, itchy skin. Up to 30% of people with psoriasis have the joint condition, too.
Nail psoriasis: It looks similar to nail fungus with pitting, tenderness, yellowing, and separation of the nail bed, with gunk between your skin and nail. The majority of people with nail psoriasis have other types, too. In fact, 80% to 90% of them have plaque psoriasis.
So, What Causes Psoriasis?
With every type of psoriasis, your skin cell turnover is 10 times faster than the normal rate. Your body is pumping out skin cells too quickly, causing them to pile up on skin’s surface and form thick patches that appear as dense, scaly, red, irritated, and inflamed plaques. But the big question is why does this happen? It’s not completely clear, but the various types of psoriasis are thought to be caused by a perfect storm of an immune dysfunction, genetics, plus at least one other environmental trigger or risk factor. So, let’s break them down one by one.
An Overactive Immune System
Psoriasis is considered an autoimmune condition. This means your immune system is a bit overzealous, causing immune cells (T cells) to start attacking healthy tissue—in this case, your skin—as if it was an invader. The “attack” causes an inflammatory cascade as white blood cells go to war with skin cells, causing them to grow more quickly and thickly than they should. In turn, this results in the formation of those painful psoriatic patches.
If a relative—parent, grandparent, sibling—has this skin condition, you’re more likely to develop it yourself. According to the National Psoriasis Foundation, if either Mom or Dad has psoriasis, you’ve got a 10% chance of having it, too. If both parents have it, your chances increase to 50%.
So, what exactly is the genetic link? Researchers have discovered about 25 gene variants that can up your chances of developing psoriasis and the overactive immune system that drives it. For example, there’s a gene called HLA-Cw6 that is strongly associated with psoriasis, especially guttate psoriasis. IL36N is another gene that’s specifically associated with pustular psoriasis, and researchers have discovered a gene called CARD14 that can cause plaque psoriasis once it’s activated by an environmental trigger.
That last part seems to be an important part of the psoriasis puzzle, especially when you consider that 10% of people are born with a psoriasis-inducing gene, but only 2% to 3% of the population develops it. Experts believe psoriasis doesn’t stem from genes alone. You need an outside factor to turn on the gene, which brings us to our next point.
Environmental Triggers and Other Risk Factors
These things aren’t considered all-out causes on their own, but if you already have the underlying genetic component or an overactive immune system, these factors may activate the condition, causing a psoriasis flare for the very first time (as well as subsequent flares in the future). These factors include:
An infection: A common cold, strep throat, tonsillitis, earache, bronchitis, or respiratory infection can bring on your first psoriasis flare-up, usually two to six weeks after you get the infection. It’s typically a bacterial infection that brings on guttate psoriasis. In most cases, guttate clears on its own after two to three weeks, but as many as 40% of people will wind up with chronic plaque psoriasis after a guttate outbreak. (An infection is what reality star Kim Kardashian says led to her psoriasis.)
Being overweight: People with psoriasis have a greater chance of being overweight. Experts say it’s somewhat of a chicken-or-egg scenario—they aren’t sure which causes which. But there’s some evidence to suggest that it’s the extra pounds that can have your skin seeing red. Studies have shown that a high BMI earlier in life is correlated with psoriasis later on. It could be that obesity raises the level of inflammation in your body, which then triggers the inflammatory skin disease. Also typically, the more you weigh, the worse your psoriasis.
Your mental well-being: Stress is some powerful stuff; you know this. It’s well-documented that stress hormones can bring on inflammation, triggering a number of conditions, including psoriasis. Depression and anxiety seem to play a role, too. A study in Journal of the European Academy of Dermatology and Venereology found that severely depressed women were twice as likely to develop psoriasis. It’s often a vicious cycle: The pain and stigma that comes along with psoriasis brings on more stress, anxiety, and depression, making skin worse or bringing on recurrent flares.
Smoking: More reason to kick butt? A study in JAMA Dermatology found that one in five cases of psoriasis may be caused by smoking, and there’s an especially high association between smoking and pustular psoriasis. Women who smoke more than 20 cigarettes a day are 2.5 more times more likely to develop psoriasis compared to non-smokers, and men are 1.7 times more at risk. You might also be scratching your skin if your parents smoked when you were a kid: A study in the American Journal of Epidemiology found that children exposed to second-hand smoke had a greater risk of developing psoriasis later in life.
Skin trauma: Burning your neck while using your curling iron, getting ears or body parts pierced, or even a tattoo can bring on new plaques. It’s called the Koebner phenomenon, in which psoriatic patches can appear after a skin injury. Studies suggest it stems from a disruption in the skin barrier, its protective outermost layer.
Alcohol: Beer drinkers, beware: A prospective study in the Archives of Dermatology followed female nurses for 14 years and found that those who drank just 2.3 non-light beers (or more) a week had an increased risk of developing psoriasis compared to non-drinkers. In this study, light beer, white and red wine, and liquor didn’t pose the same risk. However, alcohol in general is thought to both induce and aggravate inflammation, so it can not only bring on your first episode, but make an existing case worse.
What Makes Psoriasis Worse?
Speaking of making a bad situation worse, if you already have the chronic condition, certain things can increase its severity or trigger a recurrence, even if you’ve been in remission (the medical term for symptom-free) for a while. The most common triggers are:
Medications: If you already have psoriasis, certain prescription meds may make it worse or bring on a flare while you’re taking them, or after you stop. These drugs include:
Inderal (propranolol) for high blood pressure
Indomethacin, a nonsteroidal anti-inflammatory used for arthritis
Lithium (prescribed for bipolar disorder)
Prednisone, prescribed for various conditions that cause inflammation
Quinidine, a heart medication
If you have psoriasis, talk to your doctor before taking a new prescription drug to see if there is a skin-friendly alterative. It's not always an option, and unfortunately, even if you do discontinue a medication that appears to be worsening your skin condition, that doesn’t guarantee flares won’t occur in the future.
Staying indoors: When you’re in the midst of a flare-up, it’s tempting to lock yourself in your bedroom and wait for it all to go away. But shunning the sun can make your flare last longer. There’s evidence that sunlight can help alleviate a psoriasis breakout. The sun’s UVB rays can help slow the rapid cell turnover. But because the sun can also burn skin and increase your risk of skin cancers, experts suggest still wearing sunscreen and keeping exposure time short.
Skin scratching: Raking your itchy skin with your nails can make psoriasis worse and trigger new lesions in those who already have the disease. And breaking the skin’s barrier through excessive scratching can trigger new plaques and increase your risk of infection.
Inflammatory foods: While the research is somewhat limited, scientists believe certain foods can increase inflammation, including high-glycemic carbs, red meat, dairy, gluten, and nightshade produce (tomatoes, eggplants, eggplants, and pepper). Moving to an anti-inflammatory diet rich in low-glycemic carbohydrates (fruits, vegetables, whole grains) and omega fatty acids (salmon, olive oil) may alleviate some psoriasis symptoms. A study in JAMA Dermatology touts the Mediterranean diet for lessening the severity of the skin condition. And a survey of over 1200 psoriasis patients published in Dermatology and Therapy calls out the virtues of the Pagano diet (more fruits and veggies, less grains, meat, seafood, dairy, and eggs).
Cold weather: The evidence here is mostly anecdotal, but many people say their skin acts up when the temperature dips. One study in Journal of the American Academy of Dermatology found more cases tend to clear in the summer versus the winter. Doctors think it’s a combo platter of winter factors—cold air, dry heat, and less sunlight—that aggravate the condition in some people.
It’s important to note that what sets off one person’s psoriasis might not affect another’s at all. Be your own detective to ID your specific triggers. If your psoriasis acts up before your wedding, an important job interview, or a big presentation, stress is likely a trigger for you. If it rears its ugly head while you’re taking certain medications, they could be a cause. Knowing your personal triggers so you can avoid them (if possible) may help you ward off a future flare-up—or at least lessen its severity.
- Psoriasis Basics: National Psoriasis Foundation. (n.d.). “About Psoriasis.” psoriasis.org/about-psoriasis
- Genes and Psoriatic Disease: National Psoriasis Foundation. (n.d.). “Genes and Psoriasis.” psoriasis.org/research/genes-and-psoriatic-disease
- HLA-Cw6 and Psoriasis: British Journal of Dermatology. (2018). “HLA-Cw6 and Psoriasis.” ncbi.nlm.nih.gov/pubmed/29072309
- What Triggers Psoriasis: National Psoriasis Foundation. (n.d.). “Causes and Triggers”. psoriasis.org/about-psoriasis/causes
- Psoriasis Causes: American Academy of Dermatology. (n.d.). “Psoriasis: Causes.” aad.org/psoriasis-causes
- Obesity and Psoriasis: Mediators of Inflammation. (2019). “Biomarkers of Inflammation in Obesity-Psoriatic Patients.” ncbi.nlm.nih.gov/pmc/articles/PMC6558610/
- Depression and Psoriasis: Journal of the European Academy of Dermatology and Venereology. (2013). “Depression and the Risk of Psoriasis in US Women.” ncbi.nlm.nih.gov/pmc/articles/PMC4198730/
- Psoriasis Triggers: American Academy of Dermatology. ( n.d.) “Are Triggers Causing Your Psoriasis Flare-Ups?” aad.org/flare-triggers
- What Is Koebner Phenomenon?: National Institutes of Health. (n.d.). “Koebner Phenomenon.” ncbi.nlm.nih.gov/pubmed/21396563
- Alcohol and Psoriasis: Archives of Dermatology. (2010). “Alcohol Intake and Risk of Incident Psoriasis in US Women: A Prospective Study.” dovepress.com/psoriasis-and-alcohol-peer-reviewed-fulltext-article-PTT#ref-CIT0027
- Diet and Psoriasis: The Journal of Clinical and Aesthetic Dermatology. (2014). “Diet and Dermatology.” ncbi.nlm.nih.gov/pmc/articles/PMC4106357/
- Patient-reported Psoriasis Diet: Dermatology and Therapy. (2017). “Dietary Behaviors in Psoriasis: Patient-Reported Outcomes from a U.S.” ncbi.nlm.nih.gov/pmc/articles/PMC5453925/
- Mediterranean Diet and Psoriasis: Journal of Transitional Medicine. (2015). “Nutrition and Psoriasis: Is There Any Association Between the Severity of the Disease and the Mediterranean Diet.” ncbi.nlm.nih.gov/pmc/articles/PMC4316654/
- Cold Weather and Psoriasis: Journal of the American Academy of Dermatology. (2015). “Seasonal Variation of Acne of Psoriasis: A 3-Year Study Using the Global Assessment Severity Scale.” jaad.org/article/S0190-9622(15)01740-5/fulltext
- Family History and Psoriasis: Clinical and Experimental Dermatology. (2014). “Familial Aggregation of Moderate to Severe Plaque Psoriasis.” onlinelibrary.wiley.com/doi/abs/10.1111/ced.12401