Most people with psoriasis report that no particular event or illness preceded or brought about their condition, but several well-known triggers include stress, strep infection, and some medications. Although the likelihood for familial transmission may not seem significant, there is a definite genetic predisposition for psoriasis. Etiological factors of this disease are unclear. Known precipitating factors include trauma infection (haemolytic streptococcal infection) and endocrine changes.
What are the causes of psoriasis?
Psoriasis is a chronic skin disorder that affects 1% to 3 % of the world's population. It is characterized by periodic flare-ups of well defined red patches covered by a silvery, flaky scale on the extensor surfaces and the scalp. There are several variations of psoriasis but the most common type is chronic plaque psoriasis. The exact cause of psoriasis is unknown, but it is believed that a combination of several factors contribute to the development of this disease.
Immune System Causes of Psoriasis
In a normally functioning immune system, white blood cells produce antibodies to foreign invaders such as bacteria and viruses. In psoriasis, however, some white blood cells cause the body to fight normal tissue in the skin and, sometimes, joints. These white blood cells also produce chemicals that aid in healing and fighting infective agents.
These white blood cells also produce an abnormally large amount of "healing" chemicals that actually cause more inflammation in the skin and joints.
Genetic Causes of Psoriasis
Often, a person with psoriasis has a parent or grandparent who also has the condition. Researchers estimate that a person with one affected parent has about a 10% chance of also having psoriasis. Having two parents with psoriasis increases the chances to about 30%.
How Weather affects Psoriasis
Cold, dry winter weather tends to trigger a flare-up of psoriasis symptoms. In contrast, sunlight and humid, sunny climates are, as a rule, helpful - particularly in mild cases. However, hot, humid environments may make severe cases of psoriasis worse.
Stress Triggers of Psoriasis
Psoriasis itself causes stress, especially severe psoriasis. And stress makes psoriasis symptoms all the more severe. Many people with psoriasis report a direct link between the severity of their skin inflammation and their stress levels. This often leads to a self-perpetuating problem.
Infection Triggers of Psoriasis
As psoriasis is a product of a faulty immune system, it isn't surprising that events that stimulate the immune system trigger the disorder. Injuries such as burns, cuts, and bruises can also start psoriasis. Infections, particularly strep infections, also activate the body's natural defenses, and psoriasis often develops just after an infection.
How Skin Injury affects Psoriasis?
Sometimes even mild injuries to the skin such as abrasions can trigger a psoriasis flare. This is called the koebner phenomenon, and may be the reason that psoriasis tends to frequently affect the elbows and knees.
Drugs that cause Psoriasis
Some medications, including those used to treat people with high blood pressure or heart disease or those used to treat bipolar disorder have been found to worsen psoriasis symptoms. Medications used to prevent or treat malaria may also trigger psoriasis.