Psoriasis is a common skin disorder that produces thick red plaques covered with silvery scales. The most common areas affected are the scalp, elbows, knees, and lower back, although any skin surface may be involved. It can also occur in the nails and body folds.
Psoriasis is not contagious and cannot be passed from person to person, but it can occur in members of the same family.
Psoriasis usually begins in early adulthood or later in life. In most people, the rash is limited to a few patches of skin; in severe cases, it can cover large areas of the body. The rash can heal and come back again throughout a person's life.
What are the symptoms of psoriasis?
Psoriasis starts as small red bumps, which enlarge and become scaly. The skin appears thick, but bleeds easily if the scales are picked or rubbed off.
In addition, the rash may produce:
- Pitted, cracked, crumbly or loose nails
How can I find out if I have psoriasis?
If you have a rash that is not healing, seek medical advice for evaluation of the rash to determine if it is psoriasis.
Psoriasis signs and symptoms
The signs of psoriasis vary depending on the type you have. Some common signs for plaque psoriasis - the most common variety of the condition - include:
- Plaques of red, inflamed skin, often covered with loose, silver-coloured scales. These plaques may be itchy and painful and sometimes crack and bleed. In severe cases, the plaques of irritated skin will grow and merge into one another, covering large areas.
- Disorders of the fingernails and toenails, including discolouration and pitting of the nails. The nails may also begin to crumble or detach from the nail bed.
- Plaques or crust on the scalp.
- Small areas of bleeding where the involved skin is scratched.
Psoriasis can also be associated with psoriatic arthritis, which causes pain and swelling in the joints. The Psoriasis Association estimates that between 5% and 7% of people with psoriasis have psoriatic arthritis, but this figure rises to about 40% in people who have severe psoriasis.
What causes psoriasis?
The exact cause of psoriasis is unknown, but it is believed that a combination of factors contributes to the development of the disease. An abnormality in the immune system causes inflammation in the skin, triggering new skin cells to develop too quickly. Normally, skin cells are replaced every 28 to 30 days. With psoriasis, new cells grow and move to the surface of the skin every three to four days. The build-up of old cells being replaced by new cells creates the silver scales of psoriasis.
What causes psoriasis outbreaks?
No one knows what causes psoriasis outbreaks. The severity and frequency of outbreaks vary with each person. Outbreaks may be triggered by a number of factors, including:
- Skin injury (for example, cuts, scrapes or surgery)
- Emotional stress
- Streptococcal infections