Psoriasis comprises red, scaly patches of skin, which usually have very well defined edges, appear covered by silvery flaky surface [1]. These patches, which are sometimes referred to as plaques, usually itch or feel sore. The redness is explained by impressive growth and dilation of superficial blood vessels [2]. They most often occur on the elbows, knees, other parts of legs, scalp, lower back, face, palms, and soles of the feet, but they can occur on skin anywhere on the body [3]. The disease may also affect the fingernails, the toenails, and the soft tissues of the genitals and inside the mouth [4]. It is often symmetrical, affecting both sides of the body. Psoriasis is often so mild it is barely noticed by the affected person, but it can occasionally be so severe that the patient must be admitted to hospital for treatment. The disease occurs in all age groups, primarily affecting adults. The most common ages for psoriasis to first appear are in the late teens and in the 50s. It affects men and women equally, although in children, girls are more commonly affected than boys [5]. Being characterized as dermatological disease, psoriasis is a non- contagious lifelong skin disease and also not an outcome of poor hygiene. Unfortunately it is often overlooked or dismissed because it is not typically life threatening [6].

Depending on the variability in morphology, distribution, severity and cause, they are divided into different types. Some can occur independently or at the same time as other variants, or one may follow another. Most common is the plaque psoriasis which starts off in small areas, then gradually enlarge and develop thick, dry plaque. They usually appear symmetrically, that is, in the same areas on opposite sides of the body. Eventually separate patches may join together to form larger areas as the disorder develop. In some cases, the patches can become very large and cover wide areas of the back or chest (known as geographic plaques because they resemble maps). Plaque psoriasis persists for long periods. Gutate psoriasis, from the Greek word "gutta" meaning droplet, includes teardrop-shaped patches 1-10 mm in diameter, usually distributed on the trunk and often on the extremities but can also occur on the head [7]. Gutate psoriasis can also develop in patients who have already had another form of psoriasis. Pustular psoriasis is characterized by white, sterile pustules surrounded by red skin. It tends to follow a cycle-reddening of the skin followed by formation of pustules and scaling. The pus consists of white blood cells. There are two types of pustular psoriasis, generalized pustular psoriasis (von Zumbusch) and palmo-plantar pustulosis (PPP). Generalized pustular psoriasis is rare and represents active, unstable disease. This form is very widespread and the eruptions often occur in repeated waves lasting days or weeks. PPP causes pustules on the palms and soles; it is uncertain whether it really is a form of psoriasis [8].