Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 19 1 2020 02 01 18 26 Javad Fadaee Department of Immunology, Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Maryam Khoshkhui Department of Immunology, Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Maryam Emadzadeh Clinical Research Unit, Mashhad University of Medical Sciences, Mashhad, Iran Seyed Isaac Hashemy Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Reza Farid Hosseini Department of Immunology, Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Farahzad Jabbari Azad Department of Immunology, Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran Hamid Ahanchian Department of Paediatric, Allergy and Immunology, Faculty of Medicine, Mashhad University of Medical Sciences, Iran Fahimeh Lavi Arab Department of Immunology, Immunology Research Center, Mashhad University of Medical Sciences, Mashhad, Iran 2018 11 01 2019 06 01 Substance P (SP) is a neurotransmitter emitted from neurons that plays a role in the pathogenesis of itching conditions including chronic urticarial (CU). The present research aims to investigate the serum level of S.P among CU patients and compare them with healthy subjects and explore how it correlates with the severity of urticaria. The present research was conducted on 87 CU patients who visited the allergy clinic of Ghaem Hospital, Mashhad, Iran from October 2017 to June 2018. Besides, 86 healthy subjects were recruited as the control group. Background information of patient was collected including age, sex, duration of the disease and the co-occurrence of angioedema. S.P serum level was measured in two groups by ELISA method. In the patients group, the autologous serum skin test (ASST) was performed along with the urticaria evaluation questionnaire include Urticaria Activity Score 7 (UAS7), Urticaria Control Test (UCT) and Chronic Urticaria Quality of Life (CU-Q2OL). Among the patients, the SP serum level showed to be about two times higher than the healthy subjects (p˂0.001). SP showed to be increased as patients’ age grew (p=0.010). In patients with a positive ASST, SP level was higher (p=0.012). No correlation was found between SP and the presence of angioedema among patients. There was no correlation between the SP serum level and the scores obtained from urticaria evaluation questionnaires. SP among CU patients was higher than healthy subjects. SP was also higher among female, older and positive ASST patients. The SP value was not correlated with the severity of urticaria, angioedema. In conclusion, Using SP antagonist drugs could be a potential treatment for chronic urticaria. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/2178