What is psoriasis?

Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silvery scales.

These patches normally appear on your elbows, knees, scalp and lower back, but can appear anywhere on your body. Most people are only affected with small patches. In some cases, the patches can be itchy or sore.

Psoriasis affects around 2 per cent of people in the UK. It can start at any age, but most often develops in adults under 35 years old. The condition affects men and women equally.The severity of psoriasis varies greatly from person to person. For some people it's just a minor irritation, but for others it can have a major impact on their quality of life.Psoriasis is a long-lasting (chronic) disease that usually involves periods when you have no symptoms or mild symptoms, followed by periods when symptoms are more severe.


Why it happens

People with psoriasis have an increased production of skin cells.

Skin cells are normally made and replaced every three to four weeks, but in psoriasis this process only lasts about three to seven days. The resulting build-up of skin cells is what creates the patches associated with psoriasis.

Although the process isn't fully understood, it's thought to be related to a problem with the immune system. The immune system is your body's defence against disease and infection, but for people with psoriasis, it attacks healthy skin cells by mistake. Psoriasis can run in families, although the exact role that genetics plays in causing psoriasis is unclear.

Many people's psoriasis symptoms start or become worse because of a certain event, known as a "trigger". Possible triggers of psoriasis include an injury to your skin, throat infections and using certain medicines.

The condition isn't contagious, so it can't be spread from person to person.


Treating psoriasis

There is no cure for psoriasis, but a range of treatments can improve symptoms and the appearance of skin patches.

In most cases, the first treatment used will be a topical treatment, such as vitamin D analogues or topical corticosteroids. Topical treatments are creams and ointments applied to the skin.

If these aren't effective, or your condition is more severe, a treatment called phototherapy may be used. Phototherapy involves exposing your skin to certain types of ultraviolet light.In severe cases, where the above treatments are ineffective, systemic treatments may be used. These are oral or injected medicines that work throughout the whole body.

(Source: NHS Choices).


Side effects of topical corticosteroids


The most common side effect of topical corticosteroids is a burning or stinging sensation when the medication is applied. However, this usually improves as your skin gets used to the treatment.

Less common side effects can include:

• worsening of a pre-existing skin infection

• folliculitis – inflamed hair follicles

• thinning of the skin – this can make the affected skin more vulnerable to damage; for example, you may bruise more easily 

• stretch marks – which are likely to be permanent, although they'll probably become less noticeable over time

• contact dermatitis – skin irritation caused by a mild allergic reaction to the substances in a particular topical corticosteroid

• acne, or worsening of existing acne 

• rosacea – a condition that causes the face to become red and flushed

• changes in skin colour – this is usually more noticeable in people with dark skin

• excessive hair growth on the area of skin being treated  

Side effects are more likely if you're:

• using a more potent corticosteroid

• using it for a very long time, or over a large area

The elderly and very young are more vulnerable to side effects.If potent or very potent topical corticosteroids are used for a long time or over a large area, there's a risk of the medication being absorbed into the bloodstream and causing internal side effects, such as:

• decreased growth in children

Cushing's syndrome (hypercortisolism), a collection of symptoms caused by very high levels of a hormone called cortisol in the body.

The symptoms of Cushing's syndrome include:

• weight gain

• thinning skin that bruises easily

• reddish-purple stretch marks on the thighs, stomach, buttocks, arms, legs or breasts

• fat deposits that develop in the face, causing it to become round

• muscle or bone weakness 

• decreased interest in sex (loss of libido)

 (Source: NHS Choices)