Causes

Why people develop psoriasis is not fully understood, although it appears to be caused by a problem with the immune system where white blood cells called T cells, which are normally activated to fight infections, become activated against healthy skin cells instead.

As part of this process the T cells release chemicals called cytokines, which stimulate inflammation (redness) and make skin cells divide at a much faster rate than normal.

The skin cells then build up and cause the typical thickened, scaly patches of psoriasis.

It is not clear what causes the immune system to become activated against healthy skin cells. Psoriasis can run in families so it may have a genetic cause. In fact, around a third of people with psoriasis have a relative who also suffers from the condition.

Although psoriasis plaques may look infected they aren’t and are not contagious either. Other people cannot ‘catch it’ by touching the affected areas of your skin.

Triggers

Triggers are factors that lead to a worsening or reappearance of skin symptoms in someone with psoriasis. Common triggers are:²

Stress: has been shown to trigger psoriasis or to aggravate it.

Injury to the skin: e.g. cut, graze or sunburn

Infection: Some infections, such as a sore throat, may trigger a certain type of psoriasis, known as guttate psoriasis.

Medication: Some medications have been found to trigger psoriasis or flare-ups in some people.

If you think a medication may be affecting your psoriasis, talk to your doctor, nurse practitioner or pharmacist before making any changes.

See Living with Psoriasis for more tips on recognising your triggers and how to deal with them.