Psoriasis is a common skin condition that causes skin redness and irritation. Most people with psoriasis have thick, red skin with flaky, silver-white patches called scales.

See also: Guttate psoriasis

Plaque psoriasis

Psoriasis is a very common condition. The disorder may affect people of any age, but it most commonly begins between ages 15 and 35.

The condition cannot be spread to others.

Psoriasis seems to be passed down through families. Doctors think it probably occurs when the body's immune system mistakes healthy cells for dangerous substances. See also: Inflammatory response

Skin cells grow deep in the skin and normally rise to the surface about once a month. In persons with psoriasis, this process is too fast (about 2 weeks instead of 4 weeks) and dead skin cells build up on the skin's surface.

The following may trigger an attack of psoriasis or make the condition more difficult to treat:

• Bacteria or viral infections, including strep throat and upper respiratory infections
• Dry air or dry skin
• Injury to the skin, including cuts, burns, and insect bites
• Some medicines, including antimalaria drugs, beta-blockers, and lithium
• Stress
• Too little sunlight
• Too much sunlight (sunburn)
• Too much alcohol

In general, psoriasis may be severe in people who have a weakened immune system. This may include persons who have:

• AIDS
• Autoimmune disorders (such as rheumatoid arthritis)
• Cancer chemotherapy

Up to one-third of people with psoriasis may also have arthritis, a condition known as psoriatic arthritis.

Psoriasis can appear suddenly or slowly. In many cases, psoriasis goes away and then flares up again repeatedly over time.

People with psoriasis have irritated patches of skin. The redness is most often seen on the elbows, knees, and trunk, but it can appear anywhere on the body. For example, there may be flaky patches on the scalp.

The skin patches or dots may be:

• Itchy
• Dry and covered with silver, flaky skin (scales)
• Pink-red in color (like the color of salmon)
• Raised and thick

Other symptoms may include:

• Genital lesions in males
• Joint pain or aching (psoriatic arthritis)
• Nail changes, including nail thickening, yellow-brown spots, dents (pits) on the nail surface, and separation of the nail from the base
• Severe dandruff on the scalp

Psoriasis may affect any or all parts of the skin. There are five main types of psoriasis:

• Erythrodermic -- The skin redness is very intense and covers a large area.
• Guttate -- Small, pink-red spots appear on the skin.
• Inverse -- Skin redness and irritation occurs in the armpits, groin, and in between overlapping skin.
• Plaque -- Thick, red patches of skin are covered by flaky, silver-white scales. This is the most common type of psoriasis.
• Pustular -- White blisters are surrounded by red, irritated skin.

Your doctor will look at your skin. Diagnosis is usually based on what the skin looks like.

Sometimes, a skin biopsy is done to rule out other possible conditions. If you have joint pain, your doctor may order x-rays.

The goal of treatment is to control your symptoms and prevent infections.

In general, three treatment options are used for patients with psoriasis:

• Topical medications such as lotions, ointments, creams, and shampoos
• Body-wide (systemic) medications, which are pills or injections that affect the whole body, not just the skin
• Phototherapy, which uses light to treat psoriasis

Most cases of psoriasis are treated with medications that are placed directly on the skin or scalp:

• Cortisone creams and ointments
• Creams or ointments that contain coal tar or anthralin
• Creams to remove the scaling (usually salicylic acid or lactic acid)
• Dandruff shampoos (over-the-counter or prescription)
• Moisturizers
• Prescription medicines containing vitamin D or vitamin A (retinoids)

If you have an infection, your doctor will prescribe antibiotics.

You may try the following self-care at home:

• Oatmeal baths may be soothing and may help to loosen scales. You can use over-the-counter oatmeal bath products. Or, you can mix 1 cup of oatmeal into a tub of warm water.
• Sunlight may help your symptoms go away. Be careful not to get sunburned.
• Relaxation and antistress techniques may be helpful. The link between stress and flares of psoriasis is not well understood, however.

Some people may choose to have phototherapy.

• Phototherapy is a medical treatment in which your skin is carefully exposed to ultraviolet light.
• Phototherapy may be given alone or after you take a drug that makes the skin sensitive to light.
• Phototherapy for psoriasis can be given as ultraviolet A (UVA) or ultraviolet B (UVB) light.

Persons with very severe psoriasis may receive medicines to suppress the body's immune response. These medicines include methotrexate or cyclosporine. (Persons who have psoriatic arthritis may also receive these drugs.) Retinoids such as acitretin can also be used.

Newer drugs called biologics specifically target the body's immune response, which is thought to play a role in psoriasis. These drugs are used when other treatments do not work. Biologics approved for the treatment of psoriasis include:

• Adalimumab (Humira)
• Alefacept (Amevive)
• Etanercept (Enbrel)
• Infliximab (Remicade)
• Stelara

See: Psoriasis support group

Psoriasis is a life-long condition that can be controlled with treatment. It may go away for a long time and then return. With appropriate treatment, it usually does not affect your general physical health.

• Arthritis
• Pain
• Severe itching
• Secondary skin infections
• Side effects from medicines used to treat psoriasis
• Skin cancer from light therapy

Call your health care provider if you have symptoms of psoriasis or if the skin irritation continues despite treatment.

Tell your doctor if you have joint pain or fever with your psoriasis attacks.

If you have symptoms of arthritis, talk to your dermatologist or rheumatologist.

Go to the emergency room or call the local emergency number (such as 911) if you have a severe outbreak that covers all or most of your body.

There is no known way to prevent psoriasis. Keeping the skin clean and moist and avoiding your specific psoriasis triggers may help reduce the number of flare-ups.

Doctors recommend daily baths or showers for persons with psoriasis. Avoid scrubbing too hard, because this can irritate the skin and trigger an attack.

Gottlieb A, Korman NJ, Gordon KB, Feldman SR, Lebwohl M, Koo JY, et al. Guidelines for the management of psoriasis and psoriatic arthritis. Section 2. Psoriatic arthritis: overview and guidelines of care for treatment with an emphasis on biologics. J Am Acad Dermatol. 2008;58:851-864.

Menter A, Korman NJ, Elmets Ca, Feldman SR, Gelfand JM, Gordon KB, et al. American Academy of Dermatology guidelines of care for the management of psoriasis and psoriatic arthritis. Section 3. Guidelines of care for the management and treatment of psoriasis with topical therapies. J Am Acad Dermatol. 2009;60:643-659.

Menter A, Gottlieb A, Feldman SR, Voorhees ASV, Leonardi CL, Gordon KB, et al. Guidelines for the management of psoriasis and psoriatic arthritis. Section 1. Overview of psoriasis and guidelines of care for the treatment of psoriasis with biologics. J Am Acad Dermatol. 2008;5:826-850.

Stern RS. Psoralen and ultraviolet a light therapy for psoriasis. N Engl J Med. 2007;357(7):682-690.