**6. Selenium**

Selenium is an essential trace element with immune-modulating and anti-proliferative properties, with an influence over the immune response whether through a change in the expression of cytokines and respective receptors or by making immune cells more resistant to oxidative stress (Celerier et al., 1995; Roy et al., 1992; Spallholtz et al., 1990). Moreover, data indicates that patients with inflammatory skin diseases, skin cancer, malignant melanoma and cutaneous T-cell lymphoma have low concentrations of selenium (Clark et al., 1984; Deffuant et al., 1984; Hinks et al., 1987; Michaelsson & Edqvist, 1984).

The low concentration of selenium found in patients with psoriasis may be a risk factor for the development of the disease. However, there are few studies on the role of this element in the pathogenesis (Hinks et al., 1987; Fairris et al., 1989; Michaelsson et al., 1989; Harvima et al., 1993; Pinton et al., 1995; Azzini et al., 1995). Low levels of selenium are related to the severity of psoriasis and may occur due to low food intake or excessive flaking of the skin (Serwin et al., 2003). Serwin et al. (2003) found that selenium levels were significantly lower in patients with a diagnosis of psoriasis for more than three years in comparison to healthy volunteers (38.69 vs 48.41; p < 0.05).

Kharaeva et al. (2009) demonstrated for the first time that the combination of conventional therapy and supplementation with vitamin E, co-enzyme Q10 and selenium resulted in an improvement in the clinical condition of patients with severe psoriasis as well as a reduction in oxidative stress. Supplementation using inorganic forms of selenium (sodium selenite and selenate) is also reported to lead to clinical improvement in patients with psoriasis (Fairris et al., 1989; Pinton et al., 1995).
