It appears as pink or red raised patches of skin covered with silvery scales. These patches look very distinct from the rest of the skin because they have a well-defined edge around them. They are called ‘plaques’. These plaques have a scaly surface and may range in size from tiny to very large. The plaques are caused by abnormal skin cell replacement. Normally, skin replaces its outermost layer ( called epidermis) because the cells get rubbed off while you go about your daily life. In people with Psoriasis, the epidermal cells are replaced too quickly that Psoriasis sufferers produce new skin cells 7 times faster than normal i.e., In psoriasis, the skin renews itself in four days instead of normal 28 days. The cells that come to the surface are not properly formed and get heaped up into the plaques. Underlying blood vessels are also damaged, causing the redness that often occurs in psoriasis. Some people with psoriasis also experience itching.

White blood cells that move into the plaques (blisters) can form pustules in the epidermis. These blisters or pustules may appear on the soles of the feet and palms of the hands. These same changes can occur in the nails, which may become thickened and damaged, and contain tiny pits. A minority of people with psoriasis can also develop joint problems- for further information on this see ‘Psoriasis and other disease’.

Psoriasis can occur on any part of the body although elbows, knees and the scalp are usual sites. There is often accompanying irritation. Some parts of the body do not have this typical scale. These are areas where two skin surfaces come together as in the natural skin creases and folds e.g. the groin and genital area and underneath women's breasts. Psoriasis, in these areas can look bright red and shiny rather than scaly.