What Causes Plaque Psoriasis to Develop or Worsen?

A Complex Interaction Between Genes and Your Environment

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Chronic plaque psoriasis—the most common type of psoriasis—causes red patches covered by a thick, silvery scale to form on a person's scalp, elbows, knees, and/or lower back.

But who develops plaque psoriasis is not just random. In fact, there are a number of risk factors, some within a person's control, like smoking, and others not, like a person's DNA. It's also good to know that there are some factors that cannot give you psoriasis, despite common misconceptions.

For instance, you cannot get psoriasis from a friend or partner who has it, as psoriasis is not contagious. Psoriasis is also not caused by poor hygiene, another myth.

Family History

Family history is the strongest risk factor for developing plaque psoriasis. This means that if a person has one parent with psoriasis, their likelihood of developing psoriasis is higher than a person whose parents don't have psoriasis. A person's chance of developing psoriasis is even greater if both parents have it. 

This all being said, a person can still develop psoriasis if he or she does not have a parent with it. Similarly, just because a person has one or more parents with psoriasis does not mean they will one hundred percent develop it. In other words, genes are not everything when it comes to psoriasis.

Rather, in order to develop psoriasis, scientists believe that a person needs exposure to one or more environmental factors that triggers or activates one or more "psoriasis genes"— a complex interplay between a person's genetic makeup and their environment.


Smoking is an example of an environmental risk factor for developing plaque psoriasis, and both former and current smokers are at risk. In addition, a person's risk of developing psoriasis increases the longer he or she has smoked, and the more he or she smokes on a daily basis. People with plaque psoriasis who smoke also have more severe disease than those who do not smoke.

Second-hand smoke exposure at home has also been found to be a risk factor for developing psoriasis.

The good news is that the risk of developing psoriasis decreases once a person stops smoking—and the longer a person is smoke-free, the lower this risk becomes.

The link between smoking and psoriasis is complex, and there are likely multiple factors involved. One theory is that smoking increases free radicals in the body, which can damage cells and trigger the development of psoriasis. Also, since oxidative stress (the process by which free radicals are made) is already increased in people with psoriasis, smoking may worsen a person's disease—meaning a higher percentage of the body is affected and the plaques are more severe (more red, thicker plaques, more scale).


Infection is another environmental risk factor that alters a person's immune system, which can subsequently lead to a psoriasis flare. Types of infection particularly linked to psoriasis include HIV and strep throat. The bacterial infection strep throat is more commonly tied to guttate psoriasis, but it can worsen plaque psoriasis.


Obesity increases the risk of psoriasis, with plaques classically forming in a person's skin folds. While the precise "why" underlying the connection between obesity and psoriasis is still unclear, one leading theory is that since fat tissue stimulates the production of various inflammatory markers called cytokines, having a lot of fat tissue (obesity) can worsen psoriasis, which is already an inflammatory-driven skin condition.

The good news is that scientists are working hard to better understand the obesity-psoriasis link, especially since obesity puts people at risk for developing other serious medical conditions like type II diabetes and heart disease.

It's interesting to note that while obesity more commonly develops before psoriasis, it may occur the other way around. In this case, when a person with psoriasis later becomes obese, there may be a behavioral component involved. Social isolation, especially avoiding gyms or swimming pools, where plaques may be visible, can lead to weight gain.

Skin Trauma

Another risk factor for plaque psoriasis is skin trauma—this is called the Koebner phenomenon, in which a psoriasis plaque forms at the site of skin injury. It occurs in about 1 in 4 people who have psoriasis and may occur from anything that traumatizes the skin like sunburns, bug bites, surgical cuts, allergic reactions, or needle pricks from vaccines or tattoos. 

Other Risk Factors

Other risk factors that can trigger plaque psoriasis development include certain medications like:

  • lithium (used to treat bipolar disorder and can worsen existing psoriasis)
  • beta blockers (for example, Inderal used for a number of medical conditions like treating high blood pressure and preventing migraines )
  • certain nonsteroidal anti-inflammatories (for example, Indomethacin)
  • antimalarial medications

Alcohol too has been linked to both psoriasis development and a worsening of existing psoriasis, although the scientific evidence behind it is not as strong as other factors.

Psychological stress is another known trigger of psoriasis. The mechanism by which stress in life, like a change in work position or a new boss, triggers or worsens existing psoriasis is unclear. In very general terms, it may be that some people have an abnormal hormonal response to stress that leads to an alteration of their immune system. 

Diet and weather changes (like cold air) have also been cited as risk factors for psoriasis, although the science behind it is still evolving. That being said, if you notice certain foods worsen your skin plaques, avoiding those foods is prudent. On that note, be sure to discuss any diet with your doctor first to ensure it's safe, and you are getting adequate nutrition.

A Word From Verywell

The development and course of chronic plaque psoriasis are influenced by a number of factors, and what affects one person's psoriasis may or may not affect someone else's psoriasis. The good news is that there are a number of treatments available to help you manage your condition. You too can take an active role in your skin health by minimizing your exposure to certain triggers like skin trauma and medications linked to psoriasis, avoiding smoking, and maintaining a normal weight.


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