Introduction:The skin is the typically and predominantly affected organ in patients after allogeneic hematopoietic stem cell transplantation (alloHSCT). The supportive therapy in patients after alloHSCT includes especially ultraviolet protection and the use of emollients. Aim: Due to the lack of studies regarding epidermal barrier function in patients with alloHSCT, our aims were to monitor dermatologically patients 1 year after the procedure with special emphasis on epidermal barrier function and to evaluate the properties of epidermal barrier function in patients with confirmed chronic GvHD (cGvHD). Material and methods: Our pilot study included 30 patients after alloHSCT and 20 healthy controls. In the group of patients after alloHSCT there were 10 individuals who were monitored dermatologically (including evaluation of skin, mucosae, nails and hair) within 1 year after the procedure (subgroup 1) and 20 patients with previously confirmed cGvHD (subgroup 2). We evaluated transepidermal water loss (TEWL), skin hydration and skin color. The clinical assessment and all noninvasive evaluations in patients included in subgroup 1 were performed before (at baseline) and 3, 6, 9 and 12 months after the procedure, while in subgroup 2 they were performed once. Results: In subgroup 1 we did not observe significant differences between baseline results and periods of assessments in TEWL values or corneometry, erythema and melanin measurements. In subgroup 2 the highest TEWL values and the lowest corneometry results were observed in patients with sclerodermoid chronic cutaneous GvHD in comparison to patients with lichenoid chronic cutaneous GvHD and patients with cGvHD but without skin lesions. TEWL values and melanin level were significantly higher in patients with cGvHD than in controls. Conclusions: Our pioneer observations proved the disturbed epidermal barrier function among patients after al-loHSCT. Therefore it seems that proper skin care, including photoprotection, should be recognized as a crucial component in long-term management of these patients.