Measuring the Severity of Psoriasis
Severity of psoriasis ranges from one or two flaky inflamed patches to widespread pustular psoriasis that can be life threatening. The skin is usually categorized as mild to severe depending on the extent of the psoriasis to help determine treatment.

Psoriasis is divided into three degrees of severity: mild, moderate and severe. About 75 percent to 80 percent of people with psoriasis have what is considered mild disease, and about 20 percent to 25 percent have moderate to severe psoriasis. These categories are useful for selecting what treatments might be appropriate for individuals with psoriasis.

The physical measure of severity is based on how much skin on the body is affected by psoriasis. As a general rule of thumb, the palm of the hand represents 1 percent of the body's surface.

Severity can also hinge on how psoriasis affects a person's quality of life. If psoriasis covers only a small area yet is serious enough to be disabling—for example, bad psoriasis of the hands or feet—it could be considered a severe case of the disease. back to top

Mild Psoriasis
Most cases of psoriasis are limited to less than 2% of the skin. People with psoriasis on less than 2 percent of their body are considered to have a mild case. Generally, isolated patches of psoriasis are found on the knees, elbows, scalp and hands and feet. Topical treatments—including moisturizers and over-the-counter and prescription creams, ointments and shampoos—are usually sufficient to keep the psoriasis in check.

Moderate Psoriasis
Moderate psoriasis is defined as affecting between 2 percent and 10 percent of the body's surface. Psoriasis may appear on the arms, legs, torso, scalp and other areas. Appropriate therapies include topical treatments, phototherapy and oral medications, depending on the location and extent of the psoriasis and other individual factors.

Severe Psoriasis
In general severe psoriasis affects over 10% of the body. Wide-spread psoriasis (erythrodermic psoriasis and generalized pustular psoriasis) can be life threatening. Fortunately these occurrences are rare. Only about 400 people die annually from complications of severe psoriasis Psoriasis covering more than 10 percent of the body is considered severe. Extensive areas of skin may be covered with psoriasis plaques or pustules, or widespread erythrodermic psoriasis can cause severe peeling of the skin. People with severe psoriasis are more likely to develop psoriatic arthritis. Powerful treatments, including phototherapy, oral medications or a combination of these, are usually necessary to manage severe psoriasis.