Vitamin D in children with atopic dermatitis

Atopic dermatitis (AD) is one of the most common inflammatory skin diseases, with a prevalence of up to 15%-20% in children and 2%-10% in adults. Patients with AD have genetically determined risk factors that affect the barrier function of the skin and immune responses that interact with environmental factors. Recently, there has been increasing awareness of the importance of vitamin D, a potential factor, in the development and progression of atopic diseases including AD. Furthermore, some reports suggested that vitamin D deficiency impairs epithelial integrity, leading to increased and inappropriate mucosal exposure to antigens promoting sensitization. Even though numerous studies favor strong associations of vitamin D deficiency during pregnancy and infancy with allergies, high vitamin D intake might be harmful according to conflicting results of other trials. The growing body of the literature indicates an inverse relationship between the severity of AD and vitamin D levels. Animal studies, case reports, randomized clinical trials, and birth cohort studies have suggested that vitamin D may alleviate the symptoms of AD through immune-modulation of the innate and adaptive immune system. Moreover, some studies have shown that in individuals with AD with low vitamin D level, repletion of vitamin D results in decreased severity of diseases. However, all these results have prompted the question of which time, dose, duration, or mode of application of vitamin D might be appropriate in children with AD. Further large cohort studies and clinical trials are warranted to assess the role of vitamin D in the prevention and treatment of AD in children.