Psoriasis occurs when skin cell turnover is quick and cells are replaced more quickly than usual.
Body produces new skin cells in the deepest layer of skin. These skin cells gradually move up through the layers of skin until they reach the outermost level, where they die and flake off. This whole process normally takes around 3 to 4 weeks.
However, in people with psoriasis, this process only takes about 3 to 7 days. As a result, cells that are not fully mature build up rapidly on the surface of the skin, causing flaky, crusty patches covered with scales.
Common psoriasis triggers include:
- An injury to the skin, such as a cut, scrape, insect bite, or sunburn (this is called the Koebner response)
- Drinking excessive amounts of alcohol, smoking; stress, hormonal changes, particularly in women—for example, during puberty and the menopause;
- Certain medicines—such as lithium, some antimalarial medicines, anti-inflammatory medicines, including ibuprofen, and ACE inhibitors (used to treat high blood pressure);
- Streptococcal. Throat infections can develop guttate psoriasis, in some people
- Other immune disorders, such as HIV, which cause psoriasis to flare up or appear for the first time.
Psoriasis is not contagious, so it cannot be spread from person to person.