Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silvery scales. The condition is not infectious and most people are affected only in small patches on their body.

Psoriasis affects around 2% of people in the UK. It can start at any age, but most often develops between the ages of 11 and 45.

The severity of psoriasis varies greatly from person to person. For some people, it is just a minor irritation, but for others it has a major impact on their quality of life.

Psoriasis is a long-lasting (chronic) disease that can return at any time. There may be times when you have no symptoms or very mild symptoms, followed by times when the symptoms are severe.

Read more about the symptoms of psoriasis.

Outlook

There is no cure for psoriasis, but a range of treatments can improve symptoms and the appearance of the affected skin patches.

Find out more about treating psoriasis.

What happens to the skin?

Skin cells have a life cycle. Your body produces new cells in your deepest skin level. These skin cells gradually move up through the layers of your skin until they reach the outermost level. Then they die and flake off. The whole process normally takes around 21 to 28 days.

In psoriasis, this process speeds up and only takes two to six days. As a result, cells that are not fully mature build up rapidly on the surface of the skin, causing red, flaky, crusty patches covered with silvery scales. These patches are easily shed.

Read about the causes of psoriasis.

Psoriasis can occur on any part of the body, but is most common on the elbows, knees, lower back and scalp. It can cause itching and burning.

Want to know more?

• The Psoriasis Association: what is psoriasis?
• British Association of Dermatologists: an overview of psoriasis
• PAPAA: about psoriasis

Most cases of psoriasis go through cycles, causing problems for a few weeks or months before easing or stopping.

There are several different types of psoriasis. Normally, people have only one form of psoriasis at a time, although two different types can occur together. One type may change into another type or may become more severe.

Common types of psoriasis

Common types of psoriasis are:

Plaque psoriasis

This is the most common form, accounting for 80% of cases. Its symptoms are dry, red skin lesions, known as plaques, that are covered in silver scales. They normally appear on your elbows, knees, scalp and lower back but can appear anywhere on your body. The plaques can be itchy, sore or both. In severe cases, the skin around your joints may crack and bleed. 

Guttate psoriasis

This normally occurs after a streptococcal throat infection and is more common among children and teenagers. It causes small (less than 1cm or 1/3 inch) drop-shaped sores on your chest, arms, legs and scalp. There is a good chance that guttate psoriasis will disappear completely, but some people go on to develop plaque psoriasis.

Scalp psoriasis

This can occur on parts of your scalp or on the whole scalp. It causes red patches of skin covered in thick silvery-white scales. Some people find scalp psoriasis extremely itchy, while others have no discomfort. In extreme cases it can cause hair loss, although this is usually only temporary.

Nail psoriasis

This affects your nails, causing them to develop tiny dents or pits, become discoloured and grow abnormally. Often nails can become loose and separate from your nail bed. In severe cases, your nails may crumble.

Inverse (flexural) psoriasis

This affects areas of the skin that are in folds or creases, such as the armpits, groin and the skin between the buttocks and under the breasts. It can cause large, smooth red patches in some or all of these areas. Inverse psoriasis is made worse by friction and sweating, so it can be particularly uncomfortable in hot weather.

Pustular psoriasis

Pustular psoriasis is a rarer type of psoriasis that causes pus-filled blisters (pustules) to appear on your skin. Different types of pustular psoriasis affect different parts of the body.

Generalised pustular psoriasis or von Zumbusch psoriasis

This causes pustules on a wide area of skin, which develop very quickly. The pus consists of white blood cells and is not infected. The pustules may reappear every few days or weeks in cycles. During the start of these cycles, von Zumbusch psoriasis can cause fever, chills, weight loss and fatigue (see erythrodermic psoriasis, below).

Palmoplantar pustular psoriasis

This causes pustules to appear on the palms of your hands and the soles of your feet. The pustules gradually develop into circular brown scaly spots, which then peel off. Pustules may reappear every few days or weeks.

Acropustulosis

This causes pustules to appear on your fingers and toes. The pustules then burst, leaving bright red areas that may ooze or become scaly. These may lead to painful nail deformities.

Erythrodermic psoriasis

Erythrodermic psoriasis is a rare form of psoriasis that affects nearly all the skin on the body. This can cause intense itching or burning. Erythrodermic psoriasis can cause your body to lose proteins and fluid. This can lead to serious illnesses such as infection, dehydration, heart failure, hypothermia and malnutrition.

Want to know more?

• PAPAA: scalp psoriasis
• PAPAA: nail psoriasis
• PAPAA: pustular psoriasis

The exact cause of psoriasis is unknown, but it is known that your immune system plays a part. Your immune system is your body's defence against disease and helps fight infection.

If you have psoriasis, T-cells (which are found in the blood and are part of your body's defence system) start to attack healthy skin cells by mistake. This triggers the immune system to produce new skin cells and also more T-cells.

The cycle of skin cell production becomes faster and faster. Skin cells are created and then die in the space of five to six days, rather than the normal 28 days. The dead skin cells build up on the surface of your skin in thick, scaly patches.

Genetics

Psoriasis runs in families. One in three people with psoriasis has a close relative with the condition.

The exact role that genetics plays in causing psoriasis is unclear. Research studies have shown that many different genes are linked to the development of psoriasis. It is likely that different combinations of genes may make people more vulnerable to the condition. However, having these genes does not necessarily mean that you will develop it.

Psoriasis triggers

Many people's psoriasis symptoms start or become worse because of a certain event, known as a trigger. Knowing your triggers may allow you to avoid a flare-up of psoriasis. Common triggers include:

• an injury to your skin such as a cut, scrape, insect bite or sunburn (this is known as the Koebner response)
• alcohol
• smoking
• stress
• certain medicines such as lithium, some antimalarial medicines, anti-inflammatory medicines including ibuprofen, ACE inhibitors (used to treat high blood pressure) and beta blockers (used to treat congestive heart failure)
• throat infections. In some people, usually children and young adults, a form of psoriasis called guttate psoriasis (which causes smaller pink patches, often without a lot of scaling) develops after a streptococcal throat infection. However, most people who have streptococcal throat infections do not develop psoriasis
• other immune disorders, such as HIV, which cause psoriasis to flare up or to appear for the first time

Treatment overview

Treatments are determined by the type and severity of your psoriasis and the area of skin affected. Your GP will probably start with a mild treatment, such as topical creams (which are applied to the skin), and then move on to stronger treatments if necessary.

A wide range of treatments is available for psoriasis, but identifying which treatment is most effective can be difficult. Talk to your GP if you feel a treatment is not working or you have uncomfortable side effects.

Treatments fall into three categories:

• topical: creams and ointments that are applied to your skin
• phototherapy: your skin is exposed to certain types of ultraviolet light
• oral and injected medication: medicine that reduces the production of your skin cells, including biological treatments that target specific parts of the immune system

Often, different types of treatment are used in combination.

Your treatment for psoriasis may need to be reviewed regularly. You may want to make a care plan (an agreement between you and your health professional) as this can help you manage your day-to-day health.

Want to know more?

• PAPAA: psoriasis treatments
• What is a care plan?

Topical treatments

Topical treatments are creams and ointments that you apply to the affected areas of skin. These initial treatments, also called first-line treatments, are used to treat mild to moderate psoriasis. They are all that some people need to control their condition.

If you have scalp psoriasis, a combination of shampoo and ointment may be recommended.

Topical corticosteroids

Topical corticosteroids are commonly used to treat mild to moderate psoriasis in certain areas of the body, such as on the face or body folds (armpits and groin). The treatment works by reducing inflammation. This slows the production of skin cells and reduces the symptoms of itching.

Topical corticosteroids range in strength from mild to very strong. Only use topical corticosteroids when recommended by your GP. Stronger topical corticosteroids can be prescribed by your doctor and should only be used on small areas of your skin or on particularly thick patches. Overusing topical corticosteroids can lead to skin thinning.

Vitamin D analogues

Vitamin D analogue creams are one of the most common treatments for mild to moderate psoriasis. They work by slowing the production of skin cells. They also have an anti-inflammatory effect.

Vitamin D analogues are cleaner to use than other treatments. Types of vitamin D analogues include calcipotriol, calcitriol and tacalcitol. There are very few side effects, as long as you do not use more than the recommended amount.

Vitamin D analogues are often used in combination with topical corticosteroids.

Dithranol

Dithranol has been used for over 50 years to treat plaque psoriasis. It has been shown to be effective in suppressing the production of skin cells and has few side effects. However, it can burn the skin if it is too concentrated.

It is typically used as a short-term treatment under hospital supervision as it stains everything it comes into contact with, including skin, clothes and bathroom fittings. It is applied to your skin (while wearing gloves) and left for 10 to 60 minutes before being washed off.

Dithranol can be used in combination with phototherapy (see below).

Tazarotene

Tazarotene contains a chemical similar to vitamin A (retinoid), which slows the production of skin cells. It is used in the treatment of moderate plaque psoriasis. It is applied once a day.

The most common side effect of tazarotene is skin irritation around the area of application. Tazarotene cannot be used during pregnancy or if you are breastfeeding, as it could be harmful to the baby. It is not recommended for children or teenagers.

Coal tar

Coal tar is a thick, heavy oil and is probably the oldest treatment for psoriasis. How it works is not exactly known, but it can reduce scales, inflammation and itchiness. Coal tar can stain clothes and bedding and has a strong smell. It can be used in combination with phototherapy (see below).

Want to know more?

• The Psoriasis Association: first-line treatments for psoriasis
• The British Association of Dermatologists: topical treatments for psoriasis
• PAPAA: emollients and psoriasis

Phototherapy

Phototherapy uses natural and artificial light to treat psoriasis. Artificial light therapy can be given in hospitals and some specialist centres. You will usually need to be under the care of a dermatologist to receive phototherapy.

UVB phototherapy

Ultraviolet B (UVB) phototherapy uses a wavelength of light that is invisible to human eyes. The light slows down the production of skin cells and is an effective treatment for guttate or plaque psoriasis that has not responded to topical treatment. Each session only takes a few minutes but you may need to go to hospital three times a week for six to eight weeks.

Most machines used in the UK are TL01 narrow band UVB.

Psoralen plus ultraviolet A (PUVA)

For this treatment, you will first be given a tablet containing compounds called psoralens, or psoralen may be applied directly to the skin. This makes your skin more sensitive to light. Your skin is then exposed to a wavelength of light called ultraviolet A (UVA). This light penetrates your skin more deeply than ultraviolet B light.

This treatment may be used if you have severe psoriasis that has not responded to other treatment. Side effects of the treatment include nausea, headaches, burning and itchiness. Long-term use of this treatment is not encouraged as it can increase your risk of developing skin cancer.

Combination light therapy

Combining phototherapy with other treatments often increases its effectiveness. Some doctors use UVB phototherapy in combination with coal tar, as the coal tar makes the skin more receptive to light. Combining UVB phototherapy with dithranol cream may also be effective (this is known as Ingram treatment).

Want to know more?

• The Psoriasis Association: ultraviolet treatment
• The British Association of Dermatologists: phototherapy
• PAPAA: psoriasis and phototherapy

Oral and injected medication

You will normally only be prescribed tablets or injections if your psoriasis is severe and other treatments have not worked. These medications can be very effective in treating psoriasis but they all have potentially serious side effects.

All the oral and injected medicines for psoriasis have benefits and risks. Before starting oral medication, talk to your GP or dermatologist about your treatment options and any risks associated with them.

Methotrexate

Methotrexate decreases the production of skin cells and suppresses inflammation. It is taken as a tablet or by injection. It is used to treat pustular psoriasis, psoriatic erythroderma and extensive plaque psoriasis.

The drug can cause nausea and affects the production of blood cells. Long-term use can cause liver damage. People who have liver disease should not take methotrexate. Do not drink alcohol when taking methotrexate.

Methotrexate can be very harmful to a developing baby, so it is important that women use contraception and do not become pregnant while they take this drug and for three months after they stop.

Methotrexate can affect the development of sperm cells, so men should not father a child during treatment and for three weeks afterwards.

Acitretin

Acitretin is an oral retinoid that reduces the production of skin cells. It is used to treat severe psoriasis that has not responded to other treatments. It has a wide range of side effects, including dryness and cracking of the lips, dryness of the nasal passages, loss of hair and, in rarer cases, hepatitis.

Acitretin can be very harmful to a developing baby, so it is important that women use contraception and do not become pregnant while they take this drug and for two years after they stop taking it.

Ciclosporin

Ciclosporin is a medicine that suppresses your immune system (immunosuppressant). It was originally used to prevent transplant rejection but has proved effective in treating all types of psoriasis. Ciclosporin increases your chances of kidney disease and high blood pressure, which will need to be monitored.

Hydroxycarbamide

Hydroxycarbamide is sometimes used for severe psoriasis. While it is not licensed for use in the treatment of psoriasis, some people find that it helps them. It works by slowing down the production of new cells. You will need to have a full blood test before you start taking hydroxycarbamide, as well as regular blood tests during treatment.

Hydroxycarbamide can be harmful to a developing baby, so it is important that women use contraception and do not become pregnant while they take this drug and for two months afterwards. Hydroxycarbamide can affect the development of sperm cells, so men should not father a child during treatment.

Biologic treatments (targeted therapy)

Biologic treatments reduce inflammation by targeting overactive cells in the immune system. Some biologics affect T-cells, while others target the chemicals that are released by T-cells. There are several types of biologic treatment. The National Institute for Health and Clinical Excellence (NICE) has assessed them and recommended when they should be used to treat adults.

Etanercept

Etanercept is used to treat severe plaque psoriasis that has not responded to other treatments (including methotrexate and ciclosporin) or if you cannot use other treatments. Etanercept is injected twice a week and you will be shown how to do this. If there is no improvement in your psoriasis after 12 weeks, the treatment will be stopped.

The main side effect of etanercept is a rash where the injection is given. However, as etanercept affects the whole immune system, there is a risk of serious side effects including severe infection. If you had tuberculosis in the past, there is a risk that it may return. You will be monitored for side effects during your treatment.

Adalimumab

Adalimumab is used to treat severe plaque psoriasis that has not responded to other treatments (including methotrexate, ciclosporin and PUVA) or if you cannot use other treatments. Adalimumab is injected once every two weeks and you will be shown how to do this. If there is no improvement in your psoriasis after 16 weeks, the treatment will be stopped.

Adalimumab can be harmful to a developing baby, so it is important that women use contraception and do not become pregnant while they take this drug and for five months after the treatment finishes.

The main side effects of adalimumab include headaches, a rash at the injection site and nausea. However, as adalimumab affects the whole immune system, there is a risk of serious side effects including severe infections. You will be monitored for side effects during your treatment.

Infliximab

Infliximab is used to treat very severe plaque psoriasis that has not responded to other treatments (including methotrexate, ciclosporin and PUVA) or if you cannot use other treatments. Infliximab is given as a drip (infusion) into your vein at the hospital. You will have three infusions in the first six weeks, then one infusion every eight weeks. If there is no improvement in your psoriasis after 10 weeks, the treatment will be stopped.

The main side effect of infliximab is a headache. However, as infliximab affects the whole immune system, there is a risk of serious side effects including severe infections. You will be monitored for side effects during your treatment.

Ustekinumab

Ustekinumab is used to treat moderate to severe plaque psoriasis that has not responded to other treatments (including methotrexate, ciclosporin and PUVA) or if you cannot use other treatments. Ustekinumab is injected at the beginning of treatment, then again four weeks later. After this, injections are every 12 weeks. If there is no improvement in your psoriasis after 16 weeks, the treatment will be stopped.

The main side effects of ustekinumab are a throat infection and a rash at the injection site. However, as ustekinumab affects the whole immune system, there is a risk of serious side effects including severe infections. You will be monitored for side effects during your treatment.

Want to know more?

• The Psoriasis Association: systemic treatments
• The Psoriasis Association: biologic drugs for the treatment of psoriasis
• British Association of Dermatologists: etanercept
• British Association of Dermatologists: adalimumab
• British Association of Dermatologists: infliximab
• NICE guidance on etanercept and efalizumab for the treatment of psoriasis (efalizumab has been withdrawn from use because of safety concerns and NICE has suspended its guidance on this drug)
• NICE guidance on adalimumab for psoriasis
• NICE guidance on infliximab for psoriasis
• NICE guidance on ustekinumab for the treatment of adults with moderate to severe psoriasis

Healthy eating and exercise

People with psoriasis have a slightly higher risk of developing diabetes and cardiovascular disease, although it is not known why. Regular exercise and a healthy diet are recommended for everyone, not just people with psoriasis, because they can help prevent many conditions, including heart disease and many forms of cancer. Eating a healthy, balanced diet and exercising regularly can also relieve stress, which may have an effect on your psoriasis.

Want to know more?

• PAPAA: psoriasis and the heart
• PAPAA: psoriasis and smoking

Emotional impact of psoriasis

Due to the unpleasant effects that psoriasis can have on physical appearance, low self-esteem and anxiety are common among people with psoriasis. This can lead to depression, especially if the psoriasis gets worse.

Your GP or dermatologist will understand the psychological and emotional impact of psoriasis, so talk to them about your concerns or anxieties.

Want to know more?

• PAPAA: psychological aspects of psoriasis

Psoriatic arthritis

Between 10% and 20% of people with psoriasis develop psoriatic arthritis. This causes tenderness, pain and swelling in the joints and connective tissue, as well as stiffness. It commonly affects the ends of the fingers and toes. In some people, it affects the lower back, neck and knees. About 80% of people affected develop psoriatic arthritis after the onset of psoriasis, and about 20% develop it before the onset of psoriasis.

There is no single test for psoriatic arthritis. It is normally diagnosed using a combination of methods, including looking at your medical history, physical examinations, blood tests, X-rays and MRI scans.

Psoriatic arthritis can be treated with anti-inflammatory or anti-rheumatic medicines.

Want to know more?

• The Psoriasis Association: psoriatic arthritis
• PAPAA: psoriatic arthritis

Pregnancy

Psoriasis does not affect fertility and women with psoriasis can have a normal pregnancy and a healthy baby. Some women find that their psoriasis improves during pregnancy, but for some it gets worse.

Talk to your healthcare team if you are thinking of having a baby. Some treatments for psoriasis can be harmful to a developing baby, so use contraception while you are taking them. This applies to both men and women. Your healthcare team can suggest the best ways to control your psoriasis before you start trying for a family.

Want to know more?

• PAPAA: fertility, conception and pregnancy
• The pregnancy care planner

Talk to others

Many people with psoriasis have found that getting involved in support groups helps. Support groups can increase your self-confidence and reduce any feelings of isolation, and give you practical advice about living with the condition.

Want to know more?

• The Psoriasis Association: call the helpline on 0845 676 0076, Mon-Thurs 9.15am-4.45pm and Fri 9.15am-4.15pm (calls are charged at local rate)
• PAPAA: The Psoriasis and Psoriatic Arthritis Alliance: self help
• The Psoriasis Association: patient podcasts

Ray, 69, has been chairman of The Psoriasis Association for the last 33 years. He's lived with psoriasis since he was 14 and continues to treat it with coal-tar medication.

"It was 1955 and I was a 14-year-old schoolboy when my psoriasis appeared quite suddenly. I wasn’t sure what it was and didn’t have any experience of it in my family. The GP just said it might go away.

"Within about three weeks it had begun to spread. It was guttate psoriasis, so I had a pattern of little raindrop-shaped red spots that were slightly raised. This quickly spread to plaque psoriasis, and the patches began to get bigger. By then, it was scaling profusely.

"It was one of those conditions that no one knew much about. Doctors said I would just have to learn to live with it.

"I eventually got referred to a district general hospital, where I was treated with coal-tar baths and ointments. In those days it was awful stuff. It had a powerful smell and was very staining. My mother helped with the treatment and endured the laundry. I had my own linen and bed wear.

"The psoriasis came and went a little but was always present. Because of the ointments and shampoos I would smell like a newly paved road, and when it rained my hair gave off this peculiar odour.

"The psoriasis was on my body and hands but not on my face, and I could manage my scalp by combing my hair a certain way, but people always thought I had dandruff. The psoriasis improved in sunlight, so my condition was better in the summer, but it would always return.

"So I would go to hospital to have my psoriasis treated with ultra-violet light, which gave me a rather dark winter tan. This was an unusual appearance in those days, as we were an ordinary family and there was no jetting off to beaches or ski resorts. I actually received racial abuse a couple of times from people who thought I was Indian or Maltese.

"When I was 16, I wanted to join the Navy. After a few months of competing I managed to get through to the final stage, which was a medical examination. But then I was rejected. I was told I had a lifelong disease that was inappropriate for the conditions of service. I completely had to rethink what I was doing.

"In 1960, steroid medications came in. I would apply the steroids and then put on an occlusive polythene suit, which covered my trunk, arms and legs. I would be sweating underneath it and I smelt bad, an experience I wouldn’t wish on my worst enemy, even though it was a great innovation at the time.

"My psoriasis still flares up every now and then. Just over a year ago, it went wildly wrong. My legs were swelling and I was in a really bad way, so the doctors said I might have to go into hospital. I ended up taking ciclosporin, which suppresses your immune response. It restored me back to my normal psoriasis state.

"I now use a mild coal-tar preparation twice a day on the affected areas. It’s OK and doesn’t smell quite as bad as it used to. My wife, who I’ve been married to since 1965, has helped me with this virtually every day of our marriage. I have to get up extra early to allow enough time to apply the treatment and get to 9am meetings, and my wife gets up with me.

"I imagine there are hundreds of thousands of people who have to go through this regimen."