Dermatology A to Z


What Causes Psoriasis?

Psoriasis is a common skin disorder affecting about 1 in 40 people. In the United States, more than 4 million people have psoriasis. In some individuals, large areas of the skin are severely affected while others have only a few small patches or the condition is limited to the scalp, elbows, and/or knees. The cause of psoriasis is related to the immune system. Many people with psoriasis have relatives with the disease. Heredity probably plays a role.

In psoriasis, areas of the skin grow much faster than normal and form red, scaly patches. The scalp, elbows, and knees are the most common sites, but almost any part of the skin may become involved. Unfortunately,uncontrolled psoriasis has been associated with increased risk or heart attack and stroke. In addition, certain cases may involve arthritis or require periodic hospitalization. Psoriasis is a problem because it itches and is unsightly. Psoriasis is not contagious.

Psoriasis usually begins in young adulthood, although it can start in childhood or first appear in old age. In most cases, psoriasis is mild and limited to a few areas of the body. In a small percentage of cases, large areas of the body may become involved. Psoriasis is unpredictable. Patches may clear up by themselves and even disappear for months or years.

Flares of psoriasis can occur, and several triggering factors are known. The fall and winter months are periods when flares frequently occur. This is due to the diminished sunlight during this time. Second, stress, both emotional and physical, can elicit a flare. A strep infection is also a well-known agent that can activate psoriasis.


Psoriasis treatment varies by both the area of the body involved (scalp, trunk, extremities, groin or armpit) and the severity of the skin changes. What works in one site may be inappropriate or ineffective in another area. You should be given detailed individual instructions for your psoriasis. Diet does not affect psoriasis. Psoriasis will not cause your hair to fall out. Psoriasis is not caused by nerves although stress or emotional upset may lead to flares.

The treatment options for psoriasis include the following:

Tar preparations
Topical corticosteroids
Natural sunlight
Artificial sunlight (UVA, UVB or PUVA)
Oral medications
New Biologics

For extensive disease, oral medications (methotrexate, cyclosporine, or Soriatane) may be used. These medications have dangerous side effects and are used only in the most severe cases. They can be used only for short periods of time, and psoriasis is a life-long disease.

Additional Treatment Information

Tars and anthralins– These preparations are useful and sometimes are the only agents which will work. Unfortunately, they irritate normal skin. They are messy, smelly and will stain clothing and bed linens permanently. Anthralins should be used with caution when used in conjunction with topical steroids.

Corticosteroids– Topical steroids are the mainstay of treatment for psoriasis. The type of steroid, and, therefore, the strength of steroid, is carefully chosen by the doctor. Which one is dependent on many factors such as location of plaque, length of treatment, other therapies currently being used, and the age of the person. Do not use a steroid medication without specific instructions as to where and how often it should be applied.

Taclonex- This ointment is a combination of Dovonex and a steroid. This combination is very effective and only needs to be applied once each day. There seems to be fewer side effects as well.

Dovonex and Vectical- These vitamin D derivatives are excellent topical treatments. Often they can be used to decrease the amount of steroid placed on the skin. There are few side effects to these steroid-free ointments.

Tazorac- This is a topical retinoid that has been shown to treat psoriasis quite well and increase the length of time between outbreaks. It can also limit the need to use topical steroids. It can be very irritating to the skin and is best used in small areas.

Ultraviolet light- Natural sunlight is effective in treating psoriasis. Light booth treatment (not a tanning bed) is preferred, but can be logistically difficult to arrange. Sunlight contains the same wavelengths and type of light you receive in the booth in the physician’s office. In the office, several specific types of ultraviolet light can be used. Each is given in measured doses of light. This is done to prevent sunburn. The idea is to get enough sunlight to cause mild erythema (redness), but not get sunburned. If you are using tar or anthralin, your skin will be more sensitive to sunlight. Frequent exposures are needed from 3 times a week to as often as daily.