Psoriasis is a chronic disorder caused by the excessive production of skin cells, characterized by thick, red, scaly patches of skin called plaques. Normally, new skin cells take about a month to move to the top layer of the skin before dying and flaking off. However, in people with psoriasis, the entire cycle takes only a few days. As the layers of skin build-up, the skin becomes inflamed, causing plaques to develop on the arms, legs, trunk or scalp. While plaques can form anywhere on the skin, the most common areas are the knees and elbows.
Like most diseases, the symptoms of psoriasis can vary from mild to severe depending on the individual. While about 90% of all cases of psoriasis can be categorized as plaque psoriasis, other forms of the disease include guttate psoriasis, inverse psoriasis, pustular psoriasis and erythrodermic psoriasis. Most types of psoriasis go through cycles, alternating between periods of flare-ups and remission and include one or more of the following symptoms:
- Red patches of skin covered with silvery scales
- Dry, cracked skin that may bleed
- Small scaling spots (commonly seen in children)
- Itching, burning or soreness
- Thickened, pitted or ridged nails
- Joint pain or aching, which may be associated with psoriatic arthritis
- Genital lesions in males
- Eye burning, itching and discharge
Although the cause of psoriasis is unknown, studies suggest that it could be due to a dysfunction of the immune system. The immune system normally produces a kind of white blood cell, known as a T cell, to protect the body against disease and infection. However, in people with psoriasis, the T cells attack healthy skin cells by mistake, triggering the production of excessive skin cells and more T cells. This causes an ongoing cycle in which new skin cells grow too quickly, resulting in thick, red, scaly patches of skin. Researchers are still studying what causes the T cells to malfunction, but it is believed that it may result from a combination of genetic and environmental factors.
Psoriasis Triggers
While the biggest risk factor is having a family history of the disease, other factors may make a person more susceptible to developing the disease or causing a flare-up. Typically a flare-up starts or worsens because of a common trigger, such as the ones listed below:
- Stress
- Infections, such as strep throat or thrush
- Cold weather
- Heavy alcohol consumption
- Obesity
- Injury to the skin, such as a cut or scrape, bug bite or severe sunburn
- Smoking