People who smoke have a higher risk for developing psoriasis than the general population. Both people who smoke currently and people with a history of smoking for 30 years or more have a risk that is, on average, almost twice as high as those who have never smoked. Smoking is considered an independent risk factor for the development of psoriasis. That means if someone didn’t have any other factors to put them at risk for psoriasis, a history of smoking would still increase their chance to develop it.

Psoriasis is a chronic inflammatory autoimmune disease that is triggered by a disordered and overactive immune response. The condition causes an overproduction of skin cells, which leads to skin lesions or plaques. Symptoms include scaly, thickened patches of skin that are itchy and painful. (The latter is especially true for plaque psoriasis, the most common form of psoriasis.) During flare-ups, those patches may become infected.

Approximately 30 percent of people with psoriasis also develop psoriatic arthritis (PsA). This type of arthritis causes swollen and painful joints and tendons. Some people with PsA also experience symptoms such as pitted nails, pain, and redness in their eyes (uveitis).

Why Does Smoking Increase the Risk of Psoriasis?

Research has shown that cigarette smoking affects inflammatory, oxidative, and genetic factors that are associated with a person’s risk of developing psoriatic disease.

Smoking can signal inflammatory pathways in the immune system that are linked to psoriasis. Oxidation from smoking causes chemical reactions that can exacerbate skin diseases and damage the skin barrier. Smoking also increases the expression of genes that are associated with psoriasis. (In other words, smoking prompts genes to tell cells to make certain proteins that are linked with psoriasis.) Each of these chain of events can increase someone’s risk of developing psoriasis.

Who Is Most at Risk?

The risk of someone who smokes developing psoriasis increases depending on how frequently and how long (in years) they smoked. Women and men who smoke have similar rates of developing psoriasis, for the most part.

The risk of developing psoriasis rises according to how many cigarettes a person smokes on average each day. Compared to people who have never smoked, risk rates are as follows:

• People with a history of smoking but who no longer smoke — 1.4 times greater risk
• People who smoke 1 to 14 cigarettes per day — 1.8 times greater risk
• People who smoke 15 to 24 cigarettes each day — 2 times greater risk
• People who smoke 25 or more cigarettes per day — 2.3 times greater risk

The risk of developing psoriasis also increases according to how long a person has smoked. To measure this, a person’s number of “pack-years” is tallied. (When someone smokes one pack of cigarettes a day for a single year, they have one pack-year.) Those who have smoked 65 pack-years — or more — have been shown to have a risk for developing psoriasis that is approximately three times that of people who have never smoked.

For people who have smoked in the past, the risk of psoriasis decreases the more time that has passed since that person quit smoking. For example, women who stopped smoking for 30 or more years have a risk comparable to people who never smoked.

Smoking is believed to account for approximately 15 percent to 20 percent of all psoriasis cases.

Smoking and Disease Severity in Psoriasis

Smoking not only increases the risk of developing psoriasis, it also increases the risk of a person developing a more severe case of psoriatic disease. On average, people who smoke more than 20 cigarettes per day have more than twice the risk of developing more clinically severe psoriasis than those who smoke 10 cigarettes or fewer per day.

Furthermore, the risk for severe disease is higher among women who smoke. On average, females who have formerly or currently smoke have a 72 percent higher risk of developing severe psoriasis than people who have never smoked. By contrast, males who currently smoke or formerly smoked have approximately a 20 percent higher risk level than those who have never smoked.

Smoking, Psoriatic Arthritis, and Severe Psoriasis

People with psoriasis — particularly those with severe psoriasis — who smoke or have a history of smoking have higher rates of developing PsA. In a study of more than 94,000 females over 14 years, those who smoked in the past averaged an approximately 1.5-times higher incidence of developing PsA. Those who currently smoked showed an approximately three-times greater risk.

That same study unveiled several more noteworthy statistics. For instance, those who smoked more cigarettes per day over a longer duration of time had higher rates of PsA. And, among people who smoked for 45 or more pack-years, approximately 26 percent developed PsA — PsA that could be directly attributable to smoking. (Interestingly, people who smoked fewer than 15 cigarettes per day had slightly lower rates of PsA than people who never smoked. However, the risks of smoking to overall health — including exacerbation of psoriasis symptoms — far outweigh any potential protection against PsA.)

The study went on to show people with severe psoriasis who currently smoke had considerably higher rates of developing PsA. On average, those who smoked and had severe psoriasis developed PsA at more than five times the rate of people who never smoked.

A separate study considered more than 2,000 people with moderate to severe psoriasis who were undergoing biologic treatments for the first time. It noted smoking was associated with a decrease in the effectiveness of the treatments. That becomes problematic because it has been shown that treating psoriasis with biologic drugs can decrease a person’s risk of developing PsA. Smoking, therefore, may also be a risk for developing PsA, thanks to the negative impact it has on biologic therapies.

Secondhand Smoke and Psoriasis

Secondhand smoke can be an environmental factor in the development of psoriasis, particularly for very young children.

Studies have shown that prenatal smoke exposure and secondhand smoke exposure for infants and young children increases the risk of developing psoriasis later in life. Prenatal exposure increases someone’s risk of psoriasis by almost 60 percent. In fact, infants and young children regularly exposed to secondhand smoke have an almost 50 percent greater risk of developing psoriasis than those who weren’t.

Secondhand smoke is not a significant risk for the development of psoriasis in adults. (Secondhand smoke as an adult does pose other problems, such as an increased risk for cardiovascular disease.)

Smoking and Comorbidities

Smoking can negatively impact a person’s overall health and can accelerate the development of comorbidities (additional diseases) associated with psoriasis. In particular, people with psoriasis have increased risks for developing cardiovascular disease (heart disease), metabolic syndrome, inflammatory bowel disease, and lung cancer. The effects of smoking may contribute to the development of these comorbidities or it might worsen existing comorbidities.

Quitting Smoking

Quitting smoking can improve your health, well-being, and quality of life. Talk to your dermatologist and your health care team if you need help to stop smoking. And before using a nicotine patch to help you quit, get medical advice. Nicotine patches can exacerbate psoriasis in some people.

Talk With Others Who Understand

On MyPsoriasisTeam, the social network for people with psoriasis and psoriatic arthritis and their loved ones, more than 105,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriatic disease.

Are you living with psoriasis or psoriatic arthritis and have questions about smoking? Share your thoughts and experience in the comments below, or start a conversation by posting on your Activities page.