Atopic dermatitis is a common, chronic, relapsing, allergic skin disease characterized by stronglypruritic eczematous skin lesions. Pruritus is the hallmark of atopic dermatitis, with a significant impact on quality of life for the patients. Many patients define their disease severity by the intensity of pruritus rather than by the appearance of skin lesions. Although the pruritus is one of the most essential symptoms of atopic dermatitis, its pathophysiology is still unclear. The lack of effect of antihistamines argues against a role of histamine in causing atopic dermatitis–related pruritus. Neuropeptides, proteases, kinins, and cytokines induce itching. In the early stages of atopic dermatitis Th2 cellsplay a significant role. Interleukin-31 is a cytokine produced by T cells that increases the survival ofhematopoietic cells and stimulates the production of inflammatory cytokines by epithelial cells. Our study aim is to investigate the correlation between the serum level of IL-31 and the severity of disease.A total of 80 participants with a diagnosis of atopic dermatitis based on the Hanifin and Rajka criteriaare selected from all patients of the National Dermatology center. A questionnaire consisting of theparticipant’s general information and disease history is obtained. The severity of disease is assessed by using SCORAD (Scoring atopic dermatitis) and patients with AD will be grouped into mild (< 25 points), moderate (25-50 points) or severe (> 50 points) disease groups. Serum IL-31 is measured using ELISA from peripheral blood.The main symptoms were pruritis (91,3%) and xerosis (78,8%). The serum IL-31 and NGF was higher in severe patients while the pruritus and sleep loss were stronger in those patients. Serum IL-31 was significantly correlated to Scorad index and sleep loss (р<0,05).IL-31 could be itch biomarkers. IL-31 has a role in pathogenesis of pruritus and atopic dermatitis.