Psoriasis is usually long-lasting, returns often (chronic), and can be unpredictable. Symptoms may come on suddenly (flare) and then improve and go away (remission). This cycle continues over and over. In some cases, psoriasis may go away without treatment. But in moderate to severe cases, it is best to treat psoriasis so that it does not get worse.

Several factors can make the condition worse, depending on the type of psoriasis. These factors include cold, dry climates; stress; infection; skin injury; and certain medicines.

The severity of psoriasis is indicated by the amount of redness and scaling, the thickness of the large areas of raised skin patches (plaques), and the percentage of your skin that is affected.

Mild psoriasis causes plaques that cover a small portion of the body, such as the elbows or knees.

Moderate psoriasis causes:

• Several large areas of plaque. For example, most of the scalp may be affected.
• Plaques that may cover up to 20% of the skin (about equal to having both arms completely covered).
• Mild joint pain that is not disabling.
• Concern about plaques being visible to other people.

Severe psoriasis includes:

• Plaques that may cover large areas (20% to 30%) of the body. When determining the percent of coverage, consider that the palm of your hand equals about 1% of your body surface, and the total surface of both arms equals about 20%.
• Psoriasis on the face.
• Pustular psoriasis with large, fluid-filled plaque and severe scaling, or erythrodermic psoriasis with severe inflammation and shedding (sloughing) of the skin.
• Psoriatic arthritis, which includes ongoing joint swelling, tenderness, limitation of range of motion, or joint warmth or redness. Severe cases can result in joint destruction.

Psoriasis may persist for long periods of time without getting better or worse.

Psoriasis can cause a lot of stress and lowered self-esteem. You can get specialized treatment and emotional support from psoriasis day care centers. For more information on available resources, see the Other Places to Get Help section of this topic.

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