Research indicates that the disease may result from a disorder in the immune system. The immune system programs the white blood cells that protect the body from infection. In psoriasis, T lymphocytes (a type of white blood cell) abnormally trigger inflammation in the skin. These T cells also cause skin cells to grow faster than normal and to pile up in raised plaques on the outer surface of the skin.
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 psoriasis. About one-third of those with psoriasis can recall at least one family member with the disease.
Certain factors may trigger psoriasis.
- 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: Streptococcal sore throats may trigger a guttate psoriasis, a type of psoriasis that looks like small red drops on the skin.
Guttate psoriasis. Red drop-like lesions are found on the skin. This type of psoriasis usually occurs after a streptococcal (bacterial) infection. Image courtesy of Hon Pak, MD.
- 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:
- Lithium: Drug that may be used to treat depression
- Beta-blockers: Drugs that may be used to treat high blood pressure
- Antimalarials: Drugs used to treat malaria
- NSAIDs: Drugs, such as ibuprofen (Motrin and Advil) or naproxen (Aleve), used to reduce inflammation
- Emotional stress: Many people note an increase in their psoriasis when emotionally stressed.
- Smoking: Cigarette smokers have an increased risk of chronic plaque psoriasis.
- Alcohol: Alcohol is considered a risk factor for psoriasis. Even moderate intake of beer may trigger or worsen psoriasis.
- Hormone changes: The severity of psoriasis may fluctuate with hormonal changes. Disease frequency peaks during puberty and menopause. During pregnancy, psoriatic symptoms are more likely to improve. In contrast, flares occur in the postpartum period.
Medically Reviewed by a Doctor on 8/15/2014
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