Psoriasis is a chronic condition that causes inflammation and the accelerated production of skin cells. Skin builds up more quickly than it can shed, causing patches of thickened, scaly skin that can crack, bleed, and itch — as well as other symptoms.

Inflammation causes the discoloration of psoriasis rash, as well as the pain, swelling, and joint damage of psoriatic arthritis. There currently is no cure for psoriasis or psoriatic arthritis, although treatments can help control this disease effectively.

Here are 10 facts you should know about psoriasis if you or a loved one are living with the skin condition.

1. Psoriasis Is Considered an Autoimmune Disease

Psoriasis is an autoimmune disease. The damage in psoriasis and psoriatic arthritis (PSA) — together referred to as psoriatic disease — is caused by the body’s immune system attacking its own cells and tissues. In psoriasis, part of the immune system becomes overactive and attacks the skin. In psoriatic arthritis, it attacks the joints.

The exact cause of psoriasis is unknown, although it likely involves both hereditary and environmental factors. With advancing research, it is now recognized as an immune-mediated disease.

2. Psoriasis Is Not Contagious

You cannot catch psoriasis by touching someone who has it, 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.

3. Psoriasis Has Existed for Thousands of Years

Psoriasis has been around since ancient times and is seen even in mummies unearthed in Egypt. Back then, 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 other people could avoid them.

The ancient Greek doctor Galen gave the condition its name — “psora” means “itch” in Greek. Interestingly, tar was identified as an effective treatment option for psoriasis during this time. However, arsenic was also prescribed.

The ancient Greek doctor Galen gave psoriasis its name.

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, PsA was identified as a separate but related condition.

4. An Improved Understanding of Psoriasis Has Helped Inspire New Treatments

Understanding the underlying immune system triggers of psoriasis has led to improved treatments. These include corticosteroids and traditional immunosuppressants — such as cyclosporine and methotrexate. They also include newer biologics that specifically target the overactive pathway of the immune cells that cause inflammation and accelerate skin cell production.

5. Psoriasis Is Common

It’s estimated that 2 percent to 3 percent of people worldwide have psoriasis. In the U.S., more than 8 million people are thought to have psoriasis. Psoriasis affects people of all genders equally and is more common in white people than people of color.

More than 8 million people in the U.S. have psoriasis.

6. There Are 5 Types of Psoriasis

More than 80 percent of people with psoriasis have plaque psoriasis. Other types of psoriasis include guttate psoriasis, pustular psoriasis, inverse psoriasis, and erythrodermic psoriasis — as well as some rarer subtypes. Each type of skin psoriasis has a characteristic rash and location on the body. It’s possible to have more than one form of psoriasis at a time, and you may have different types at different points in your life.

About 30 percent of people with skin psoriasis have psoriatic arthritis. It’s possible to have PsA without skin psoriasis.

7. Psoriasis Treatments Include Topical, Oral, Injected, and Infused Medications

Psoriasis treatments are typically aimed at affecting the immune system to help calm inflammation and reduce attacks on the skin and joints. Psoriasis treatments may be applied topically to the skin (through creams and ointments), taken orally as tablets, or administered via injection or infusion.

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. Your dermatology provider can help you find the best treatment for your specific case.

8. Symptoms of Psoriasis May Come and Go

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 discolored, scaly patches of skin that can crack or bleed, dry skin, shedding skin, and itching, burning, or stinging sensations. Other symptoms may include thick, white, or silvery scales on the skin (plaques) and nails that are thick or ridged (nail psoriasis). In cases of psoriatic arthritis, symptoms can also include joint pain and swelling, as well as joint damage and deformity in advanced stages of psoriatic arthritis (arthritis mutilans).

The most common symptoms of psoriasis include discolored, scaly patches of skin that can crack or bleed, dry skin, shedding skin, and itching, burning, or stinging sensations.

9. Different Factors Can Trigger Psoriasis Flares

Psoriasis symptoms can come and go with flare-ups — periods of time with new or worsened psoriasis symptoms. Common flare triggers include stress, smoking, alcohol consumption, some medications, skin injuries, and cold, dry weather.

10. There Is No ‘Psoriasis Diet’

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 maintain a healthy weight, lower the risk of heart disease, and fight inflammation.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and their loved ones. On MyPsoriasisTeam, more than 133,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

Are you living with psoriasis or psoriatic arthritis? What do you do to manage it? Share your experience in the comments below, or start a conversation by posting to your Activities page.