en Dermathology Dermathology Original Article Original Article <span style="font-family:Times New Roman;"><span style="color:#0033ff;"><strong><em>Background</em></strong><em>:</em></span> Narrowband ultraviolet B (NB-UVB) phototherapy has been used as a common treatment for dermatologic diseases such as psoriasis and vitiligo and generally considered a safe form of therapy during pregnancy<span dir="RTL">.</span> Invitro photodegradation of folate after exposure to UVB radiation has been documented but studies on UVB-induced alternation of serum folate level have reported inconsistent results. The aim of this study was to investigate the effect of NB-UVB radiation on serum folate level.<br> <span style="color:#0033ff;"><strong><em>Methods</em></strong><em>:</em></span> In this study, serum folate levels were evaluated in patients at baseline and after 30 sessions of NB-UVB irradiation.<br> <span style="color:#0033ff;"><strong><em>Results</em></strong><em>:</em> </span>Twenty patients completed the study: 10 psoriasis, 7 vitiligo and 3 mycosis fungoides (patch stage). Mean serum folate level had significantly decreased from 2.76&plusmn;0.59 ng/ml at baseline to 1.34&plusmn;0.15 ng/ml after 30 sessions. (Mean NB-UVB cumulative dose 40.35&plusmn;16.80 j/cm², P=0.001).<br> <span style="color:#0033ff;"><strong><em>Conclusion</em></strong><em>:</em></span> Serum folate levels may decrease after long-term NB-UVB phototherapy in patients with skin disorders.</span> narrowband ultraviolet B phototherapy, folate, psoriasis, vitiligo 180 183 http://caspjim.com/browse.php?a_code=A-10-1811-1&slc_lang=en&sid=1 Azar Shirzadian kebria shirzadiank@gmail.com 100319475328460028174 100319475328460028174 Yes Department of Dermatology, Yahyanejad Hospital, Babol University of Medical Sciences, Babol, Iran Meghdad Hosseini mubmeghdad271@gmail.com 100319475328460028175 100319475328460028175 No Babol University of Medical Sciences, Babol, Iran Sorayya khafri khafri@yahoo.com 100319475328460028176 100319475328460028176 No Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran