en آلرژی و ایمونولوژی بالینی Allergy and Clinical Immunology Original Article Original Article <strong>Background</strong>: Considering the high prevalence of asthma in children and the role of indoor air humidity in the onset and exacerbation of asthma due to increased house dust mites and indoor molds, the optimal humidity range for houses with asthmatic individuals is 10 to 45%. This study was conducted to determine the indoor air humidity levels in the houses of asthmatic children living in Mashhad, northeast Iran.&nbsp;<br> <strong>Methods</strong>: This cross-sectional study was conducted from July 2018 to June 2019 at the Allergy Clinic of Akbar Children&rsquo;s Hospital, Mashhad, Iran. Sixty asthmatic children aged between 2 and 14 years were enrolled in the study. All patients who met the eligibility criteria were asked to place a device for humidity measurement in different rooms, including the bedroom, kitchen, and living room.&nbsp;<br> <strong>Results</strong>: Sixty patients were recruited in this study. The mean age was 6.83&plusmn;3.0 years (ranging from 2 to 14 years), with forty-one male patients (68.3%). The mean age of the buildings was 14.8&plusmn;17.5 years. The mean air humidity levels were 34.4&plusmn;7.4% in the living room, 36&plusmn;8% in the bedroom, and 36.1&plusmn;8.1% in the kitchen. Thirty-nine percent of the participants used air humidifiers, with most of them using cool mist-producing devices.&nbsp;<br> <strong>Conclusions</strong>: Air humidity in Mashhad was within the optimal range for asthmatic patients. According to our study, most asthmatic patients with air humidity levels exceeding 50 percent were using air humidifiers. It seems parents should be educated on the fact that using humidifiers, especially in the bedroom, may worsen asthma control.&nbsp; Children, Asthma, Humidity, House dust mite 263 268 http://jpr.mazums.ac.ir/browse.php?a_code=A-10-1171-1&slc_lang=en&sid=1 Nasrin Moazzen moazzenn@mums.ac.ir 100319475328460012827 100319475328460012827 No Allergy Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Mahbubeh Nateghi Rivashi Nateghim72.mhb@gmail.com 100319475328460012828 0009-0002-2743-6675 No Department of Pediatrics, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Javad Gaffari javadneg@yahoo.com 100319475328460012829 100319475328460012829 No Department of Allergy and Clinical Immunology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Mohammad Reza Khakzad Mashhad-mr.khakzad@gmail.com 100319475328460012830 100319475328460012830 Yes Department of Immunology, Innovative Medical Research Center, School of Medicine, Mashhad Medical Science Branch, Islamic Azad University, Mashhad, Iran. Rana Rafrishi ranatafrishi96@gmail.com 100319475328460012831 0009-0004-6564-8737 No Department of Allergy and Immunology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.   Hamid Ahanchian Ahanchianh@mums.ac.ir 100319475328460012832 100319475328460012832 No Allergy Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.