What is it?

Psoriasis is a common chronic condition affecting the skin. It is characterised by raised patches of skin called plaques. These patches are usually red, pink or purple with an overlying silvery-white scale caused by an accumulation of dead skin. They commonly occur on the elbows, knees, scalp or back, and are often accompanied by itchiness and excessive flaky skin.


Psoriasis is a separate condition from eczema, though the two are often conflated as both cause itchy patches. Psoriasis tends to develop in adulthood, occurs in parts of the body more likely to experience trauma (back of the elbow, front of the knees) and creates flaky skin. Eczema tends to develop in childhood, occurs on “flexural” surfaces (creases in the body) and is less flaky. If unsure, our diagnostic service can help you determine which condition you have.

What causes it?

People with plaque psoriasis will usually have a genetic predisposition to the condition, though environmental factors can both trigger and exacerbate the process.


A common trigger is usually localised trauma such as a scratch or an infection which leads to the activation of inflammatory cells in the skin. These inflammatory cells secrete chemicals that cause skin cells to rapidly replicate (reducing the lifespan of a skin cell from around 28 days to 3-5 days). The shortened skin lifespan leads to an accumulation of dead skin cells which further stimulates local inflammation.

How to treat it?

The principles of psoriasis treatment are to (1) suppress inflammation and (2) normalise skin-cell replication. There are several treatments that can aid this:


  1. Topical (cream-based) steroids are common first-line treatments. They work by reducing skin inflammation, thereby diminishing skin-cell turnover.

  2. Other topical treatments include substances called XXX (similar to vitamin-D) which work by reducing skin cell turnover to a normal rate.

  3. Exposure to UV light may also be an effective treatment. The UV both affects the skin cell DNA, inhibiting the replication process, as well as suppressing the immune cell function. However, UV therapy needs to be used in a controlled manner as UV light exposure can cause skin damage and lead to skin cancers.

Oral medicines may also be prescribed for the treatment of severe or stubborn cases.