Psoriasis occurs when disruptions in the immune system cause it to attack healthy cells, producing psoriasis symptoms. The condition is a symptom, rather than a cause, of immune changes.

Psoriasis is a lifelong condition that affects more than 7.5 million people in the United States. Despite the prevalence of the disease, there is still a lot to learn about what causes it.

Most treatment and management strategies for psoriasis, including medications and lifestyle changes, focus on changing effects on the immune system. Several factors also naturally affect the immune system.

This article explores five facts about the relationship between the immune system and psoriasis.

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Healthcare professionals generally consider psoriasis an autoimmune disorder, which means it develops when the immune system attacks healthy cells in the body.

In psoriasis, immune cells known as T cells attack healthy skin cells. These T cells release signals that recruit other immune cells to create an inflammatory environment within the skin.

This causes the body to produce new skin cells faster than it needs to, resulting in extra skin cells piling on top of each other. This leads to the plaques characteristic of psoriasis. These plaques are typically red or pink on light skin tones and light to dark brown, purple, or gray on darker skin tones.

However, this misdirection of the immune system may not be exclusive to the skin. Psoriasis often occurs alongside other autoimmune disorders, such as:

  • arthritis
  • alopecia
  • thyroiditis
  • vitiligo
  • inflammatory bowel disease
  • rheumatoid arthritis

Psoriasis tends to run in families, and a family history of the condition is a risk factor for the disease.

Researchers have found genes associated with the development of psoriasis in a region of the genome known as psoriasis susceptibility 1, or PSORS1. This gene accounts for up to 50% of the heritability — the genetic component — of psoriasis and is usually associated with early onset psoriasis.

Genes in this region instruct the body to build proteins that are involved in recognizing molecules called antigens, which trigger a person’s immune responses. Typically, these antigens occur on the surface of foreign invaders such as bacteria or viruses.

However, mutations in these genes can cause the immune system to incorrectly identify the body’s own cells as foreign, leading to autoimmunity.

Studies have identified several other genes that contribute to the development of psoriasis. These genes regulate many processes, including:

  • inflammation
  • T-cell activity
  • skin cell growth

Several factors associated with psoriasis may affect the immune system.


Studies suggest that a history of smoking may increase the risk of psoriasis by more than 60%. It may also reduce a person’s response to treatment.

Many toxins found in cigarette smoke may affect immune function. For example, nicotine molecules may affect certain aspects of immune system regulation, potentially changing inflammatory responses.

Cold weather

According to the National Psoriasis Foundation, cold weather is often a trigger for psoriasis. However, this may be at least partly due to less sunlight exposure during cold seasons.

Exposure to ultraviolet (UV) radiation and sunlight supports the body’s vitamin D production and regulates immune cell activity in the skin. This is why psoriasis often flares up in times of less sun exposure. Some studies suggest that taking vitamin D supplements may improve psoriasis symptoms, but more research is needed.

Phototherapy, which involves targeted exposure to UV radiation, has a long history as a successful treatment for psoriasis and other skin conditions.

During cold seasons, people are also more likely to get sick with infectious illnesses such as the flu. These types of illnesses can cause psoriasis to flare up.

Stress and anxiety

There is a close relationship between stress and psoriasis. For some people, stress makes psoriasis worse, and psoriasis causes stress.

One study found that 36% of people with psoriasis experience anxiety, while another suggested that stressful triggers may increase the risk of a psoriasis flare-up.

Although researchers are still investigating the exact mechanisms behind this relationship, there is an association between long-term stress and inflammation and increased activation of immune cells.

According to the National Psoriasis Foundation, other lifestyle and environmental triggers for psoriasis include:

  • skin injuries
  • sunburn
  • alcohol use
  • certain foods and medications

The human gut is home to a diverse ecosystem of bacteria known as the microbiome.

When the microbiome becomes dysregulated, it can cause “leakiness” in the gut, which signals to the immune system that something is wrong.

This triggers inflammation throughout the body and may lead to the development or progression of psoriasis.

There has been increasing interest in the role of anti-inflammatory diets in managing psoriasis symptoms. For example, a 2018 study found that following an anti-inflammatory Mediterranean diet was associated with less severe psoriasis.

Some of the effects of diet on psoriasis may also have associations with weight. Being overweight or having obesity is considered a risk factor for psoriasis.

The most common infectious trigger of psoriasis is streptococcal infection. Infections can trigger psoriasis through systemic inflammation.

Widespread inflammation triggers many symptoms of COVID-19, particularly severe forms of the disease, and small studies suggest that this inflammation may cause psoriasis flares in some cases.

However, although treatment of psoriasis often involves the use of immunosuppressive drugs, studies have found no additional risk for the occurrence or severity of COVID-19 symptoms associated with the use of psoriasis medications.

A study of more than 1,300 people in Turkey found that biologic psoriasis treatment was not a risk factor for COVID-19 or severe disease, reporting that 55% of those with psoriasis who had COVID-19 experienced a flare-up.

Below are several frequently asked questions relating to psoriasis and the immune system.

Do you have a weak immune system with psoriasis?

Psoriasis does not weaken the immune system; in fact, psoriasis is a product of an overactive immune system.

However, chronic inflammation due to psoriasis can increase a person’s risk of several conditions, such as heart disease and stroke.

What immune system problems cause psoriasis?

People with psoriasis have a higher risk of several autoimmune conditions, including vitiligo and diabetes. However, the link between the conditions is unclear. Psoriasis occurs due to a change in immune function, so any condition that affects the proper working order of this system may worsen symptoms or cause flares.

Does psoriasis indicate an overactive immune system?

Psoriasis is the result of an overactive immune system. Chronic inflammation in healthy tissue is the root of psoriasis symptoms.

Psoriasis is the result of an overactive, misdirected immune system. In psoriasis, a person’s immune system mistakenly attacks healthy cells, causing inflammation. This commonly presents as visible symptoms on the skin but can occur throughout the body.