Psoriasis is considered to be an autoimmune disease that results in the overproduction of skin cells. The process begins when a person's immune system fights against an infection, but the antibodies it makes continue to attack normal cells. A type of white blood cell (called a T cell) that is supposed to regulate immune response fails to do its job, triggering inflammation and abnormal skin cell growth.
Those with a family history of psoriasis have an increased chance of having the disease. Some people carry genes that make them more likely to develop psoriasis. When both parents have psoriasis, the child may have a 50% chance of developing the condition. About one-third of those with psoriasis have at least one family member with the disease.
Certain factors may trigger psoriasis. They include:
Injury to the skin: Injury to the skin has been associated with plaque psoriasis. For example, a skin infection, skin inflammation, or even excessive scratching can trigger psoriasis.
Sunlight: Most people generally consider sunlight to be beneficial for their psoriasis. However, a small minority find that strong sunlight aggravates their symptoms. A bad sunburn may worsen psoriasis.
Streptococcal infections: Some evidence suggests that streptococcal infections may cause a type of plaque psoriasis. These bacterial infections have been shown to cause guttate psoriasis, a type of psoriasis that looks like small red drops on the skin.
HIV: Psoriasis typically worsens after an individual has been infected with HIV. However, psoriasis often becomes less active in advanced HIV infection.
Drugs: A number of medications have been shown to aggravate psoriasis. Some examples are as follows:
Emotional stress: Many people see an increase in their psoriasis when emotional stress is increased.
Smoking: Cigarette smokers have an increased risk of chronic plaque psoriasis.
Alcohol: Alcohol is considered a risk factor for psoriasis, particularly in young to middle-aged males.
Hormone changes: The severity of psoriasis may fluctuate with hormonal changes. Disease frequency peaks during puberty and menopause. A pregnant woman's symptoms are more likely to improve than worsen, if any changes occur at all. In contrast, symptoms are more likely to flare in the postpartum period, if any changes occur at all.