Psoriasis causes patches of skin that are dry, red and covered in silver scales.
You should see your GP if you think you may have psoriasis.
Some people find their psoriasis causes itching or soreness.
There are several different types of psoriasis. Many people have only one form at a time. Although two different types can occur together. One form may change into another or become more severe.
Most cases of psoriasis go through cycles. These may cause problems for a few weeks or months before easing or stopping.
Plaque psoriasis (psoriasis vulgaris)
This is the most common form, accounting for about 80 to 90% of cases.
Its symptoms are dry red skin lesions, known as plaques, covered in silver scales.
They appear on your elbows, knees, scalp and lower back. But they can appear anywhere on your body. The plaques can be itchy or sore, or both. In severe cases, the skin around your joints may crack and bleed.
This can occur on parts of your scalp or on the whole scalp. It causes red patches of skin covered in thick, silvery-white scales. Some people find scalp psoriasis itchy, while others have no discomfort. In extreme cases, it can cause hair loss, although this is usually only temporary.
In about half of all people with psoriasis, the condition affects the nails. Psoriasis can cause your nails to develop tiny dents or pits. They can become discoloured or grow abnormally. Nails can often become loose and separate from the nail bed. In severe cases, nails may crumble.
Guttate psoriasis causes small drop-shaped sores on your chest, arms, legs and scalp. There's a good chance guttate psoriasis will disappear completely after a few weeks. But some people go on to develop plaque psoriasis.
This type of psoriasis sometimes occurs after a streptococcal throat infection and is more common among children and teenagers.
Inverse (flexural) psoriasis
This affects folds or creases in your skin. Such as the armpits, groin, between the buttocks and under the breasts. It can cause large, smooth red patches in some or all these areas.
Inverse psoriasis is made worse by friction and sweating. This can be particularly uncomfortable in hot weather.
Less common types
Pustular psoriasis is a rarer type of psoriasis. It causes pus-filled blisters (pustules) to appear on your skin. Different types of pustular psoriasis affect different parts of the body.
Generalised pustular psoriasis or von Zumbusch psoriasis
This causes pustules that develop quickly on a wide area of skin. The pus consists of white blood cells and is not a sign of infection.
The pustules may reappear every few days or weeks in cycles. Von Zumbusch psoriasis can cause fever, chills, weight loss and fatigue.
This causes pustules to appear on the palms of your hands and the soles of your feet. The pustules develop into circular, brown, scaly spots that then peel off. Pustules may reappear every few days or weeks.
This causes pustules to appear on your fingers and toes. The pustules then burst, leaving bright red areas that may ooze or become scaly. These may lead to painful nail deformities.
Erythrodermic psoriasis is a rare form of psoriasis that affects nearly all the skin on the body. This can cause intense itching or burning. Erythrodermic psoriasis can cause your body to lose proteins and fluid. This can lead to infection, dehydration, heart failure, hypothermia and malnutrition.
Content supplied by the NHS and adapted for Ireland by the HSE