Psoriasis a common skin problem, but not infectious
Psoriasis is a common condition where there is inflammation of the skin. It typically develops as patches (plaques) of red, scaly skin. Once you develop psoriasis it tends to come and go throughout life. A flare-up can occur at any time. The frequency of flare-ups varies. There may be times when psoriasis clears for long spells. However, in some people flare-ups occur often. Psoriasis is not due to an infection. You cannot pass it on to other people and it does not turn into cancer.
About 1 in 50 people develop psoriasis at some stage in their life. Psoriasis is more common in white people. It can develop at any age but it most commonly starts between the ages of 15 and 30 years.
There are different types of psoriasis. However, chronic plaque psoriasis (described below) is by far the most common and typical type.
CHRONIC PLAQUE PSORIASIS
Between 8 and 9 out of 10 people with psoriasis have chronic plaque psoriasis. The rash is made up of patches (plaques) on the skin. The picture above shows typical plaques of psoriasis.
Each plaque usually looks pink or red with overlying flaky, silvery-white scales that feel rough. There is usually a sharp border between the edge of a plaque and normal skin.
The most common areas affected are over the elbows and knees, the scalp and the lower back. Plaques may appear anywhere on the skin but they do not usually occur on the face.
The extent of the rash varies between different people and can also vary from time to time in the same person. Chronic plaque psoriasis can be itchy but it does not usually cause too much discomfort.
There are two variations of chronic plaque psoriasis:
- Scalp psoriasis: about half of people with chronic plaque psoriasis affecting the skin of their body will also have psoriasis affecting their scalp. The whole scalp may be affected, or there may just be a few patches. If severe, it can lead to hair loss in some people.
- Flexural psoriasis: this is also a type of chronic plaque psoriasis. It occurs in the creases of the skin (flexures) such as in the armpit, groin, under breasts and in skin folds.
In most people who have psoriasis, there is no apparent reason why a flare-up develops at any given time. However, in some people, psoriasis is more likely to flare up in certain situations. These include the following:
- Infections. Certain types of infections may cause a flare-up of psoriasis. In particular, a sore throat caused by a certain type of germ (bacterium) called Streptococcus spp. can cause a flare-up of guttate psoriasis or chronic plaque psoriasis.
- Medication. Some medicines may possibly trigger or worsen psoriasis in some cases. Medicines that have been suspected of doing this include: beta-blockers (propranolol, atenolol, etc), antimalarial medication, lithium, anti-inflammatory painkillers (ibuprofen, naproxen, diclofenac, etc), angiotensin-converting enzyme (ACE) inhibitor medicines, and some antibiotics. In some cases the psoriasis may not flare up until the medication has been taken for weeks or months.
- Trauma. Injury to the skin, including excessive scratching, may trigger a patch of psoriasis to develop. The development of psoriatic plaques at a site of injury is known as Köbner's phenomenon.
- Sunlight. Most people with psoriasis say that sunlight seems to help ease their psoriasis. However, some people notice the opposite with strong sunlight seeming to make their psoriasis worse.
- Hormonal changes. Psoriasis in women tends to be worst during puberty and during the menopause.
There is no once-and-for-all cure for psoriasis. Treatment aims to clear the rash as much as possible. However, as psoriasis tends to flare up from time to time, you may need courses of treatment on and off throughout your life. There are various treatments options. There is no 'best buy' that suits everybody. The treatment advised by your doctor may depend on the severity, site and type of psoriasis. It is not unusual to try a different treatment if the first one does not work so well. Many of the treatments are creams or ointments.
If you have severe psoriasis then you may need hospital-based treatment. Light therapy (phototherapy) is one type of treatment that can be used. If psoriasis is severe and is not helped by creams or phototherapy then a powerful medicine which can suppress inflammation is sometimes used.