Psoriasis

At a glance

  • Psoriasis leads to reddish, scaly patches of skin that may itch.
  • That can greatly affect your quality of life.
  • Depending on the severity of the symptoms, medication and UV light therapy can help.
  • In mild psoriasis, treatments applied directly to the skin are usually enough to relieve the symptoms.
  • Psoriasis comes and goes in bouts (flare-ups). It is not contagious.

Introduction

Photo of a teenage girl being examined by a doctor
PantherMedia / imagepointfr

Psoriasis is a non-contagious inflammatory disease. The main symptoms are reddish, scaly patches of skin that may itch.

It is a chronic condition that is typically associated with periods of more severe skin problems (flare-ups) followed by periods of milder skin problems or none at all. Various treatments can relieve the symptoms, but there is no cure for psoriasis.

The severity of psoriasis can vary quite a lot. In some people it is bothersome more than anything else, and they can cope with it quite well. Others feel that it has a major effect on their quality of life. The treatment and skin care can take a long time. Having visible reddened and scaly skin patches can really get to you mentally too – especially if they are on areas of your body that others can see.

Psoriasis is caused by inflammations. Sometimes the that is causing the psoriasis affects other parts of the body too, such as the joints or nails.

Symptoms

There are different types of psoriasis. The most common is plaque psoriasis (also known as Psoriasis vulgaris). 80% of people who have psoriasis have this type.

Plaque psoriasis (psoriasis vulgaris)

It is associated with clearly defined areas of slightly raised red patches with silvery, flaky skin. The patches of skin are referred to as "plaques," which is why it is called "plaque psoriasis." The plaques often develop symmetrically on both sides of the body, for example on both the left and right knee.

Plaque psoriasis can develop anywhere on the body. It typically occurs on the head, elbows, knees and back. Plaques are also often found behind the ears and on the hands, feet and belly button.

The size of the plaques varies greatly, ranging from anywhere between one and more than ten centimeters in diameter. Some people have only a few plaques on certain parts of their body. Others may have more, either on one part of their body or in several places.

In more severe cases of psoriasis or during flare-ups, the affected areas of skin may itch a lot as well. Scratching then often irritates the skin even more or even damages it. The skin on the hands and feet can become very dry and cracked too. This can be very painful – especially if the cracked skin stretches when you move or comes into contact with irritants like citric acid, for instance when squeezing a lemon.

Inverse psoriasis

Sometimes psoriasis occurs in skin folds such as the creases of skin in the groin or between the buttocks, under the armpits, in the genital area or under and between the breasts in women. That kind of psoriasis is called inverse (flexural) psoriasis. It is often less scaly because the skin in these areas generally isn't as dry and there is constant friction so not many plaques develop.

Illustration: Areas of skin affected by plaque psoriasis or inverse psoriasis – as described in the article

Areas of skin affected by plaque psoriasis or inverse psoriasis

Nail psoriasis

Sometimes the nails of people with plaque psoriasis are also affected. In nail psoriasis, small dents develop in the nails (pitted nails), the nails grow thicker, or they turn yellowish-brown ("oil drop" discoloration). The nails might also become loose.

Pustular psoriasis

In this form of psoriasis, pus-filled blisters (pustules) occur on the skin too. These pustules aren't contagious, though. Pustular psoriasis can occur on its own or together with plaque psoriasis.

Guttate psoriasis

This form of psoriasis is quite rare. It is characterized by a large-scale acute rash made up of small spots, and is most common in children and teenagers. It usually occurs one to two weeks after a certain type of bacterial infection (Streptococcal ). Guttate psoriasis may heal completely within a few weeks or months, but it can also come back or turn into plaque psoriasis.

Causes

The outermost layer of skin (epidermis) is made up of cells that divide, move to the surface of the skin, die there and harden. These cells are known as keratinocytes.

It usually takes about four weeks for keratinocytes to move up through the outermost layer of skin and be shed as dead cells. In psoriasis, they divide about ten times as quickly and it only takes four days for them to reach the surface of the skin. The dead cells can't be shed fast enough so they build up, creating thick and scaly patches of skin that flake off.

This is caused by an autoimmune response: The immune system is overly active and releases greater amounts of certain chemical messengers (known as cytokines) that trigger various inflammations. Some of these cytokines cause the keratinocyte cells to divide more rapidly. The skin is often red due to the and increased blood flow.

Illustration: Growth and shedding of skin cells – as described in the article

Growth and shedding of skin cells

Risk factors

Psoriasis is mostly caused by genetic factors. Having a family history of the disease is the greatest risk factor.

The probability that a child will develop psoriasis is about 15% if one parent has the condition, and about 40% if both parents have it.

There is no reliable test for predicting whether someone will get psoriasis. Psoriasis can't be prevented.

Prevalence

It is estimated that about 2% of the population has psoriasis – that's more than 1.5 million people in a country the size of Germany. Men and women are equally likely to get it.

Psoriasis often first arises in the first 40 years of life, particularly in teenagers or young adults. That is sometimes referred to as type 1 psoriasis. Type 2 psoriasis usually starts later on – between the ages of 50 and 70.

Outlook

It is impossible to predict how someone’s psoriasis will develop over time. The symptoms might be particularly severe and bothersome at times, and then go away or improve a lot for a while. Some people constantly have severe psoriasis, though.

Psoriasis flare-ups may be caused by things like a sunburn, a very hot shower, particular chemicals or minor skin injuries, for instance caused by scratching, tattoos or piercings.

Other triggers include emotional stress, infections and nicotine or too much alcohol. It is also thought that some medicines might act as triggers, including some malaria drugs.

Effects

The autoimmune response in psoriasis can also affect parts of the body other than the skin: It is estimated that 25% of all people who have psoriasis also have inflamed joints. This is called psoriatic arthritis. It is a good idea to seek medical advice if you think you have psoriatic arthritis. The sooner joint is discovered, the better it can be treated and the easier it is to avoid joint damage.

Psoriasis can really get to you mentally – sometimes so much that it leads to depression or an anxiety disorder. It can then be a good idea to have treatment specifically for this problem, for instance in the form of psychotherapy.

Research has also shown that people who have psoriasis are at higher risk of cardiovascular diseases. It is thought that the autoimmune response increases the risk of metabolic disorders and vascular (blood vessel) diseases. People who have psoriasis often have high blood pressure, diabetes or harmful cholesterol levels as well or are often very overweight (obese) too.

Chronic inflammatory bowel diseases such as Crohn's disease and are also somewhat more common in people who have psoriasis. One study involving about 1,700 people with psoriasis found that 2% of them had inflammatory bowel disease.

In very rare cases psoriasis can cause life-threatening complications that need to be treated in the hospital. For instance, psoriasis may spread over the entire body and then cause blood poisoning and heart failure (cardiac insufficiency). This is called erythrodermic psoriasis ("erythroderm" comes from the Greek for "red skin"). The signs of this complication include a fever, exhaustion, chills, swollen lymph nodes and a red skin rash that covers a lot of the body.

Diagnosis

Dermatologists (skin doctors) usually diagnose psoriasis on the basis of typical changes in the skin. If they aren't sure, they may take a small skin sample and examine it. This can be a good idea when it comes to inverse psoriasis, for example: It only occurs in folds of skin and usually isn't scaly, so it is sometimes mistaken for a fungal . Skin samples can help to rule out fungal infections.

Nail psoriasis is sometimes confused with a fungal nail infection. Some people have both of these conditions. To find out whether the symptoms are being caused by a fungal , a nail sample can be examined.

The doctor will also assess how severe the psoriasis is. The area of affected skin is one factor that plays a role here: Mild psoriasis affects up to 3 to 5% of the body surface area, compared to 5 to 10% in moderate psoriasis and more than 10% in severe psoriasis.

Psoriasis is also considered to be moderate or severe if

  • it occurs on the head, hands, nails, feet, or sensitive parts of the body such as the genitals, or
  • it greatly affects the person's quality of life.

Treatment

There are various treatment options for psoriasis:

  • Skin care (basic therapy): Care of the affected areas of skin using lipid-replenishing ointments, creams or lotions. This is done to keep the skin supple, protect it from injury and relieve itching. Some products also contain medications that are supposed to reduce the shedding of skin, such as urea or salicylic acid. Good skin care is recommended during periods without any skin problems, too.
  • Topical treatments (medications that are applied directly to the skin) generally provide enough symptom relief in mild psoriasis. Suitable medications include creams, ointments, lotions and foams containing steroids or vitamin D analogues.
  • Light therapy is considered for the treatment of moderate or severe psoriasis, particularly if topical treatment alone doesn't help enough. It involves shining ultraviolet light (UV light) on the plaques. The UV light reduces in the skin, and also slows the production of cells. Sometimes medications called psoralens are used in combination with light therapy. Psoralens make the skin more sensitive to light.
  • Medications that are swallowed or injected are a treatment option for moderate and severe psoriasis. They inhibit the body's immune response. Apremilast, cyclosporine, fumaric acid esters, methotrexate (MTX) and biological drugs (biologics) are commonly used for this purpose.

Other treatments haven't been scientifically proven to help in psoriasis. This is true for herbal medicines such as extracts of barberry (Mahonia aquifolium), birch bark or aloe vera, as well as dietary supplements like fish oil and omega-3 fatty acids. Because of this, medical societies don't recommend that they be used in the treatment of psoriasis.

A few studies suggest that losing weight can reduce the symptoms in people who are very overweight. Various treatments can help here.

It is sometimes claimed that a tonsillectomy (surgery to remove the tonsils) can relieve psoriasis symptoms. But no studies have shown that this surgery can prevent psoriasis or make it go away. Tonsil surgery usually isn't recommended for this purpose because the operation may cause complications such as infections, bleeding and changes to the person's voice.

Everyday life

Psoriasis can be very hard to deal with. A lot of people find it difficult to combine the extensive skin care routine and sometimes many other treatments with everyday commitments, work, family and social activities. At night the itching is often so bad that it can be difficult to sleep, leaving you tired and exhausted the next day.

Although the condition is so common, people with psoriasis are still often avoided by others – perhaps because they mistakenly assume that it is contagious. Everyday activities such as going to the hairdresser can be very stressful as a result.

Fear of how others will react can affect your quality of life and cause some people to become withdrawn. Many people with psoriasis find it helpful to talk with others who have the disease. In support groups, for example, you can share your feelings and experiences and discuss practical problems that people who don't have psoriasis often have difficulty understanding.

Further Information

When people are ill or need medical advice, they usually go to see their family doctor first. Read about how to find the right doctor, how to prepare for the appointment and what to remember.

There are many sources of help for people with psoriasis, including support groups and information centers. Many of these are organized quite differently from region to region, though. Our list of places to contact may help you to find and make use of the help you need.

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Dupire G, Droitcourt C, Hughes C et al. Antistreptococcal interventions for guttate and chronic plaque psoriasis. Cochrane Database Syst Rev 2019; (3): CD011571.

Farahnik B, Sharma D, Alban J, Sivamani RK. Topical Botanical Agents for the Treatment of Psoriasis: A Systematic Review. Am J Clin Dermatol 2017; March 13, 2017.

Farahnik B, Sharma D, Alban J, Sivamani R. Oral (Systemic) Botanical Agents for the Treatment of Psoriasis: A Review. J Altern Complement Med 2017; February 03, 2017.

Ford AR, Siegel M, Bagel J et al. Dietary Recommendations for Adults With Psoriasis or Psoriatic Arthritis From the Medical Board of the National Psoriasis Foundation: A Systematic Review. JAMA Dermatol 2018; 154(8): 934-950.

Griffiths CE, Barker JN. Pathogenesis and clinical features of psoriasis. Lancet 2007; 370(9583): 263-271.

Ko SH, Chi CC, Yeh ML et al. Lifestyle changes for treating psoriasis. Cochrane Database Syst Rev 2019; (7): CD011972.

Lebwohl M. Psoriasis. Lancet 2003; 361(9364): 1197-1204.

Nast A, Amelunxen L, Augustin M et al. Leitlinie zur Therapie der Psoriasis vulgaris (S3-Leitlinie). AWMF-Registernr.: 013-001. Update 2017.

Reich K, Krüger K, Mössner R, Augustin M. Epidemiology and clinical pattern of psoriatic arthritis in Germany: a prospective interdisciplinary epidemiological study of 1511 patients with plaque-type psoriasis. Br J Dermatol 2009; 160(5): 1040-1047.

Upala S, Sanguankeo A. Effect of lifestyle weight loss intervention on disease severity in patients with psoriasis: a systematic review and meta-analysis. Int J Obes 2015; 39(8): 1197-1202.

Weigle N, McBane S. Psoriasis. Am Fam Physician 2013; 87(9): 626-633.

World Health Organization (WHO). Global report on psoriasis. Genf: WHO; 2016.

Yang SJ, Chi CC. Effects of fish oil supplement on psoriasis: a meta-analysis of randomized controlled trials. BMC Altern Med 2019; 19(1): 354.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on April 27, 2021
Next planned update: 2024

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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