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Psoriasis is an immune-mediated condition that causes the body to make new skin cells in days rather than weeks.

There are several types of psoriasis, the most common of which is plaque psoriasis. It causes patches of thick red skin and silvery scales that are typically found on the elbows, knees, and scalp.

Psoriasis causes itchiness and irritation and may be painful. There’s no cure for psoriasis yet, but treatment can ease symptoms.

Read on to get the scoop on psoriasis causes, prevalence, symptoms, treatment options, and more.

Anyone can get psoriasis, regardless of age. But psoriasis is most likely to appear first between the ages of 15 and 35 years old. Males and females get it at about the same rate.

According to the International Federation of Psoriasis Associations (IFPA), nearly 3 percent of the world’s population has some form of psoriasis. That’s over 125 million people.

The World Health Organization noted in 2016 that the reported prevalence of psoriasis worldwide ranges between 0.09 percent and 11.43 percent, making psoriasis a serious global problem.

In the United States, it affects about 7.4 million people.

While scientists don’t know what exactly causes psoriasis, we do know that the immune system and genetics play major roles in its development.

Psoriasis usually causes patches of thick, red skin with silvery scales that itch or feel sore.

Psoriasis can show up anywhere — on the eyelids, ears, mouth and lips, skin folds, hands and feet, and nails. In mild cases, it may cause patches of dry, itchy skin on your scalp.

In severe cases, it can progress to cover large areas of your body and cause a variety of uncomfortable symptoms.

With psoriasis, red and rough skin takes on the appearance of silver scales. Your skin may also be dry and cracked, which can make it bleed. Your fingernails and toenails can become thick and pitted.

You may have occasional flare-ups followed by times when you don’t have symptoms.

Plaque psoriasis

Plaque psoriasis is the most common type of psoriasis, and can be itchy and painful. It makes up 80 to 90 percent of cases and causes red skin lesions and silver scales that can occur anywhere on the body.

Though rare, these can even appear on the inside of your mouth or on your genitals.

Scalp psoriasis

Psoriasis can also occur on your scalp. The main symptom is a dry, itchy scalp.

It’s estimated that up to 80 percent of people with psoriasis will have a flare-up on their scalp. You may also notice flakes in your hair and on your shoulders. Scratching from these symptoms can cause bleeding.

Nail psoriasis

Psoriasis of the fingernails and toenails can cause your nails to appear pitted and discolored. Your nails can get weak and crumble, and they may even separate from your nail bed.

Psoriatic arthritis

Around 30 to 33 percent of people with psoriasis go on to develop psoriatic arthritis, according to the Journal of the American Academy of Dermatology.

Joint pain, stiffness, and swelling are the main symptoms of psoriatic arthritis. Symptoms can affect any part of your body, including your finger joints and spine, and can range from relatively mild to severe.

Guttate psoriasis

This type of psoriasis can be triggered by a bacterial infection. It generally affects children and young adults, and is estimated to affect about 8 percent of people with psoriasis.

Skin sores appear on the scalp, torso, arms, and legs. The scales are finer than those from other types of psoriasis. Some people with this type have only one outbreak that clears up without treatment, while others continue to have outbreaks over time.

Inverse psoriasis

Inverse psoriasis may cause patches of red, irritated skin in body folds, such as the armpits, under the breasts, or around the genitals and groin.

Inverse psoriasis causes smooth patches of red, inflamed skin that worsen with friction and sweating. It may be triggered by a fungal infection.

Pustular psoriasis

Pustular psoriasis is a rare type of psoriasis that can come on quickly. First, your skin becomes red and tender to the touch. Within hours, pus-filled blisters appear. These blisters may clear up and come back from time to time.

Flare-ups may be triggered by infection, irritation, or even by some medications. In addition to itching, pustular psoriasis can cause:

  • fever
  • chills
  • diarrhea
  • kidney and liver problems

These issues can be severe. With one type of pustular psoriasis, Von Zumbusch, you’ll need immediate medical care as it can be life-threatening. You may need to be hospitalized to treat it.

Erythrodermic psoriasis

This rare but severe type of psoriasis can affect your whole body. It can cause severe itching and pain, and make the skin come off in sheets.

It’s estimated to affect 3 percent of people with psoriasis. Symptoms include:

  • red, peeling skin
  • itchiness
  • a burning sensation

Medications, such as corticosteroids, may trigger erythrodermic psoriasis. Other triggers include:

  • phototherapy
    treatment
  • sunburn
  • psoriasis that
    has spread

This form of psoriasis can be life-threatening and if you have this type of flare, you should see a doctor immediately.

Causes

The exact cause of psoriasis isn’t known. Research suggests that psoriasis could be an autoimmune disease, though no autoantigen that could be responsible has been defined yet.

In your immune system, it’s the job of your T cells to attack foreign organisms to keep you healthy. For those with psoriasis, the T cells mistakenly attack healthy skin cells. This leads to an overproduction of new skin cells, T cells, and white blood cells.

This all allows dead skin cells to accumulate. The accumulation creates the hallmark scaly patches seen in psoriasis.

No type of psoriasis is contagious. You can’t catch psoriasis from someone who has it.

Risk factors

Many people with psoriasis have a family history of the disease, and researchers have found some genes linked to psoriasis.

According to the National Psoriasis Foundation, you’re 10 percent more likely to get psoriasis if one of your parents has it. Your risk is even higher — 50 percent — if both of your parents have it.

Bacterial or viral infections may also be a factor. According to the Mayo Clinic, you’re at greater risk of getting psoriasis if you have HIV. Children with frequent bouts of strep throat or other recurring infections also have a higher risk. This may be due to the way these infections affect your immune system.

Certain medications may also play a role in the development of psoriasis. The following have all been linked to psoriasis:

  • lithium
  • beta-blockers
  • tetracycline
  • nonsteroidal anti-inflammatory drugs (NSAIDs)
  • malaria drugs
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Smokers have a higher risk of psoriasis. If you already have the condition, smoking may make it worse.

Areas of skin that have been injured or traumatized are occasionally the sites of psoriasis. However, not everyone who has psoriasis develops it at the site of an injury.

Obesity has also been associated with psoriasis, but the question remains: Which came first? Does psoriasis cause obesity or does obesity increase the risk of psoriasis?

There’s some evidence that obesity predisposes individuals to the development of psoriasis. So it’s important to eat healthy and maintain a healthy weight to also avoid psoriasis-related health problems such as:

Flare-ups may also be brought on by emotional stress or triggered by certain drugs, weather, or alcohol.

Despite its considerable effect on quality of life, psoriasis is underdiagnosed and undertreated. If you suspect you may have psoriasis, contact a board-certified dermatologist who can examine your skin, nails, and scalp for signs of the condition.

In most cases, diagnosis of psoriasis is straightforward. A doctor can typically make a determination by conducting a physical exam and reviewing your medical history.

If there’s any doubt, your doctor may do a biopsy to confirm the diagnosis. Psoriatic arthritis will need additional testing.

There’s currently no cure for psoriasis, but treatment can slow down the growth of skin cells and relieve pain, itching, and discomfort.

Treatments can be divided into four main types:

  • topical
    treatments
  • light therapy
  • systemic
    medications
  • biologics

The best treatment varies by individual, taking into consideration the type of psoriasis you have, where it is on your body, and the possible side effects of medications.

For mild cases, there are a variety of over-the-counter (OTC) topical ointments that can help. There are also a number of things you can do at home that will help treat the symptoms of psoriasis.

Prescription corticosteroids can also help, but they’re often only used during flare-ups. Other topical treatments include:

  • calcipotriene (Dovonex) and calcitriol (Rocaltrol), synthetic (man-made) vitamin D that works by slowing the growth of
    skin cells
  • anthralin (Dritho-Scalp), which regulates DNA
    activity in skin cells and remove scales
  • tazarotene (Tazorac), a derivative of vitamin
    A that’s used to normalize DNA activity and decrease inflammation
  • tacrolimus (Prograf) and pimecrolimus (Elidel), that work by reducing inflammation
  • salicylic acid, which is used to get rid of
    dead skin cells
  • coal tar, which works by reducing inflammation
    and scaling
  • moisturizers, used to soothe dry skin

Light therapy and natural sunlight can also ease psoriasis symptoms. This is because light can slow skin cell growth and scaling. Phototherapy can be combined with other topical or systemic agents to enhance efficacy.

Systemic treatments impact the entire immune system. These drug options are available in oral and injectable drugs. These include:

Biologic drugs, or biologics, are drugs that target specific parts of the immune system. Typically they are prescribed for moderate to severe psoriasis and psoriatic arthritis that hasn’t responded to other treatments. Biologics at this time are given by injection or intravenous (IV) infusion.

Having psoriasis increases your risk of psoriatic arthritis. Approximately 30 to 33 percent of people with psoriasis will develop psoriatic arthritis.

Psoriasis may also increase your risk of:

While medication can reduce or clear psoriasis, anything that irritates your skin can cause psoriasis to flare — even when you use medication. Because the condition is chronic, psoriasis can significantly impact your quality of life.

The World Health Organization notes that 48 percent of people reported that their disability due to psoriasis had a modest impact on activities of daily living. Frequent bouts of psoriasis can cause people to withdraw from social situations or work. This may lead to feelings of depression.

If you have psoriasis, see your doctor as often as recommended. They can help you find a treatment plan that works for you.

Because of the risk of complications, your doctor should do regular exams and screenings to check for related conditions.

Jen Thomas is a journalist and media strategist based in San Francisco. When she’s not dreaming of new places to visit and photograph, she can be found around the Bay Area struggling to wrangle her blind Jack Russell Terrier or looking lost because she insists on walking everywhere. Jen is also a competitive Ultimate Frisbee player, a decent rock climber, a lapsed runner, and an aspiring aerial performer.