What Causes Psoriasis?

The exact cause of psoriasis is unknown. But, genetics, your immune system, and environmental factors can trigger symptoms.

Psoriasis is an autoimmune disease that causes inflammation in the body and speeds up the growth of skin cells. When this happens, the skin cells can pile up and turn into thick patches of discolored skin, which are referred to as “plaques.” 

People with psoriasis usually begin to notice their plaques develop on the knees, elbows, and scalp. Sometimes, plaques can spread to the hands, feet, and areas of the body where your skin folds (e.g., under your arms and breasts). Symptoms can develop at any age, but most people with psoriasis start developing plaques between the ages of 15 and 35.

Scientists do not yet know what causes psoriasis, as research is still underway. However, researchers do know that the condition is not contagious and that your immune system functioning and genetics play a large role in whether you will develop the condition. In some cases, environmental factors can also trigger the onset of symptoms or lead to psoriatic flare-ups.

Middle-aged woman seeing the effect of psoriasis on her chest

Jose Araujo / Getty Images

Immune System Functioning

Since psoriasis is an autoimmune condition, researchers believe that an overactive immune system speeds up skin cell growth. When the immune system is functioning properly, skin cells typically take about a month to grow completely and then shed. With psoriasis, skin cells can grow within three to five days. After the cells are done growing, instead of shedding, they pile up on the skin and develop into dry plaques. 

Research suggests that the overgrowth of skin cells occurs because of an issue with your T-cells, or white blood cells. T-cells are an important part of the immune system. They help keep you safe by fighting bacteria, viruses, and other harmful things that enter the body.

However, if you have psoriasis, your T-cells attack healthy skin cells by mistake. As a result, your body reacts by making new skin cells more frequently, which eventually turn into plaques and scales on the skin.


While people can develop psoriasis without having a family history of the disease, a 2020 study found that a family history of psoriasis and psoriatic arthritis can make you more likely to develop the condition.

Research also suggests that if you have one parent that has psoriasis, you have a 28% chance of also developing symptoms. Your likelihood of developing the condition rises to 65% when both parents have psoriasis.

What Is Psoriatic Arthritis?

Psoriatic arthritis is an autoimmune disease that typically develops in people who have psoriasis. People with psoriatic arthritis experience joint symptoms such as pain, inflammation, and stiffness.

Research about the connection between psoriasis and genetics is still ongoing. Even if you have a gene linked to psoriasis, it doesn’t always mean you will get the condition. Alternatively, there are people with psoriasis who don’t have genes associated with psoriasis but still develop symptoms. This is why experts think environmental factors can also contribute to the onset of psoriasis symptoms. 

Environmental Triggers 

In some cases, you may experience psoriasis symptoms or flare-ups due to a variety of environmental triggers. These factors can vary from person to person and not all triggers affect everyone the same way.

  • Stress: Stressful life events (e.g., job loss or divorce) and daily stressors (e.g., being stuck in traffic or studying for a big test) can cause a psoriasis flare-up. However, eliminating all stress from your life isn’t a realistic goal. Instead, using stress management techniques like meditation, exercise, or journaling, can help you manage stress better and reduce flare-ups. 
  • Injury: Cuts, scratches, and severe sunburns are all types of skin injuries that can lead to the onset of symptoms. Research shows that skin injuries can cause new plaques and lesions on the skin. This is a result of the Koebner phenomenon which suggests that injury to the skin can lead to a psoriatic flare-up.
  • Illness: Due to the autoimmune nature of psoriasis, any illness that triggers the immune system can cause symptoms. Illnesses such as strep throat, bronchitis, and ear infections may trigger a flare-up. Generally, children may be more susceptible to illness-related flare-ups. However, an illness can lead to the onset of symptoms in adults, too.   
  • Cold and dry weather: Research suggests that the lack of sunlight and humidity that is associated with colder weather can trigger psoriasis flare-ups. For some people, cold weather can lead to dry or flaky skin and worsen symptoms. If weather affects your symptoms, warmer and more humid weather can improve symptoms and reduce flares.
  • Lifestyle behaviors: Drinking alcohol, using tobacco, taking certain medications, shaving, and getting tattoos can sometimes lead to flare-ups. Each of these lifestyle factors varies from person to person. It can take some time to learn what triggers your flare-ups and that’s OK. To help you better understand what your triggers are, keeping a log of your symptoms and what may have triggered them can help.  

A Quick Review 

Like other autoimmune diseases, researchers are still investigating the exact cause of psoriasis. Here’s what they do know: a combination of an overactive immune system, a genetic link to psoriasis, having a family history, and exposure to environmental triggers like stress or illness may all contribute to the onset of symptoms. 

If you suspect that you may have psoriasis symptoms, it’s a good idea to visit your healthcare provider for an examination and a proper diagnosis

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7 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. American Academy of Dermatology Association. Psoriasis: Causes.

  3. Solmaz D, Bakirci S, Kimyon G, et al. Impact of having family history of psoriasis or psoriatic arthritis on psoriatic diseaseArthritis Care Res (Hoboken). 2020;72(1):63-68. doi:10.1002/acr.23836

  4. National Psoriasis Foundation. Psoriatic disease and the immune system.

  5. National Psoriasis Foundation. Causes and triggers.

  6. Ji YZ, Liu SR. Koebner phenomenon leading to the formation of new psoriatic lesions: evidences and mechanisms. Biosci Rep. 2019;39(12):BSR20193266. doi:10.1042/BSR20193266

  7. American Academy of Dermatology Association. Are triggers causing your psoriasis flare-ups?

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