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Psoriasis is a chronic condition that causes inflammation and the accelerated production of skin cells. Skin builds up more quickly than it can be shed, causing patches of thickened skin that crack and itch, as well as other symptoms. Inflammation causes the redness of psoriasis rash as well as the pain, swelling, and joint damage of psoriatic arthritis. There is no cure for psoriasis or psoriatic arthritis.
Psoriasis is not contagious. You cannot catch it by touching someone with psoriasis, even if they are in a flare state with visible patches. Unfortunately, fear of contagion is a common stigma that socially impacts people living with psoriasis.
Psoriasis is an autoimmune disease. In other words, the damage in psoriasis and psoriatic arthritis (together referred to as psoriatic disease) is caused by the body’s immune system attacking its own tissues. In psoriasis, the immune system attacks the skin, and in psoriatic arthritis, it attacks the joints.
The cause of psoriasis is unknown, although it likely involves both hereditary and environmental factors. Read more about causes of psoriasis.
Psoriasis has been known since ancient times, seen even in mummies unearthed in Egypt. Psoriasis was usually considered a contagious disease, and people who had it were stigmatized in many parts of the world. In some communities, people with psoriasis were forced to ring a bell as they walked, like lepers, so people could avoid them. The famed ancient Greek doctor Galen gave the condition its name; psora means "itch" in Greek. Interestingly, tar was identified as an effective treatment for psoriasis during this time period. However, arsenic was also prescribed.
In 1840, Austrian dermatologist Ferdinand von Hebra distinguished psoriasis as separate from and unrelated to leprosy. In the 19th century, sunlight was noted as an effective treatment for psoriasis. It wasn’t until the 1960s that the medical profession realized that psoriasis is an autoimmune condition. In the same decade, psoriatic arthritis was identified as a separate but related condition.
Understanding the underlying autoimmune triggers of psoriasis has led to improved treatments, from Corticosteroids and traditional immunosuppressants such as Cyclosporine and Trexall (Methotrexate) to newer biologics like Humira (Adalimumab) and Enbrel (Etanercept) that specifically target the immune cells that cause inflammation and accelerated skin cell production. Read more about treatments for psoriasis and psoriatic arthritis.
It is estimated that 2 to 3 percent of people worldwide have psoriasis. In the U.S., roughly 7.5 million people are thought to have psoriasis. Psoriasis affects women and men about equally and is thought to be more common in people of European descent.
More than 80 percent of those with psoriasis have plaque psoriasis. Other types of psoriasis include guttate psoriasis, pustular psoriasis, inverse psoriasis, and erythrodermic psoriasis. Each type of skin psoriasis has a characteristic type of rash and location on the body. It is possible to have more than one type of psoriasis.
About 30 percent of people with skin psoriasis develop psoriatic arthritis. Types of psoriatic arthritis (PsA) include spondylitis, enthesitis, and dactylitis. Types are based on which joints are involved. It is possible to have psoriatic arthritis without skin psoriasis.
Read more about different types of psoriasis.
Psoriasis treatments are typically aimed at modulating the immune system to calm inflammation and reduce autoimmune attacks on the skin and joints. Psoriasis treatments may be applied topically to the skin, taken orally, or administered via injection. Phototherapy, or light therapy, may also be helpful in some cases. Some people with psoriasis feel better when they change their diet or try complementary or alternative therapies such as acupuncture or acupressure. Read more about psoriasis treatments.
Psoriasis affects each person a little differently. Symptoms depend on the type of psoriasis and can appear or disappear at any time. Symptoms often appear near the joints – especially elbows and knees – but can also be found on the scalp, face, hands, and other parts of the body. Symptoms worsen during flares (also called exacerbations) and may subside during periods of remission.
The most common symptoms include red, scaly patches on the skin that can crack or bleed, shedding skin, and itching, burning, or stinging feeling. Other symptoms may include thick, white or silvery scales and nails that are thick or ridged. In cases of psoriatic arthritis, symptoms can also include swollen, painful joints and joint damage. Read more about psoriasis symptoms.
Psoriasis symptoms can come and go with flares. Common triggers for flares include stress, smoking, alcohol consumption, some medications, and even cold weather.
No single diet has been proven by clinical studies to improve symptoms in everyone with psoriatic disease. However, eating a healthy diet can help people with psoriasis achieve and maintain a healthy weight, lower the risk of heart disease, and fight inflammation. Read more about diet recommendations for people with psoriasis in the psoriasis treatments section.
What is the difference between psoriasis and eczema?
Both eczema and psoriasis are conditions that are visible on the skin and include red, cracked, dry skin. It is possible to have both eczema and psoriasis at the same time. Psoriasis and eczema have different causes and treatments. Read more about the differences between eczema and psoriasis.
Where does psoriasis usually show up on the body?
Different types of psoriasis affect different parts of the body. Symptoms often appear near the joints – especially elbows and knees – but can also be found on the scalp, face, hands, and other parts of the body. Read more about different types of psoriasis.
What does psoriasis look like?
Different types of psoriasis have different appearances. The majority of skin psoriasis is plaque psoriasis, characterized by patches of thickened, scaly skin that looks white or silvery. Read more about what different types of psoriasis look like.
Who treats psoriasis?
Psoriasis is commonly diagnosed and treated by a dermatologist. Psoriasis can also be treated by an internal medicine specialist. Psoriatic arthritis is usually treated by a rheumatologist.