To the editor,Dermographism is a secondary temporal linear cutaneous wheal after scratching, stroking, or rubbing the skin. The prevalence of dermographism was estimated as 4%-5% in general population1, with a higher prevalence of 24% in the pediatric population2. From previous reports, dermographism was associated with drug-induced urticaria3, hypereosinophilic syndrome4, and endocrinopathies. However, the above data were mainly derived from case reports or case-control studies of western countries. Moreover, Bolognia et al proposed that dermographism was not related to the atopy, food allergy, autoimmunity diseases5.We conducted a population-based cross-sectional study in China. The first-year college students in three universities of China who consented to participate underwent health examination and an online questionnaire survey. Diagnosis of skin diseases and inquiry of disease history were performed by dermatologists during the health examination. Dermographism was induced by a scratching test and evaluated by a dermatologist. Annual household income and parents’ educational level were determined by a self-reported questionnaire that included six given categories. Itch and pain of the skin were measured by the numeric rating scales. Sleep quality was measured by the Pittsburgh Sleep Quality Index. Symptoms of depression and anxiety were measured by the 2-item Patient Health Questionnaire and Generalized Anxiety Disorder Scale-2, respectively. Mixed logistic models were used to estimate the associations in terms of odds ratios (OR), including crude and adjusted ORs and 95% uncertainty intervals. The effect sizes were adjusted for the individual-level covariates (sex and socioeconomic indicator) and the random effects of sampling units (university). Statistical analyses were performed with SAS 9.4 (SAS Inc., Cary, USA).P <0.05 was considered statistically significant.A total of 16,167 college students was newly enrolled in three universities located in Changsha, Xiamen, and Hohhot, respectively, in 2018. Among them, 12,127 (response rate 75%) completed the questionnaire survey and health examination and were finally analyzed. The mean age of the participants was 18.3±0.8 years, and 52.7% were women. The point prevalence of dermographism was 15.6%, with no sex difference. The prevalence of grade 2–3 dermographism was 1.43%. As shown in Table 1, the prevalence of dermographism was positively associated with socioeconomic status indicators (trend P <0.001). Dermographism was significantly associated with a series of skin comorbidities (Table 2), including atopic dermatitis (adjusted OR=1.39, P =0.008), chronic urticaria (OR=2.56, P <0.001), acne vulgaris (OR=1.29,P <0.001), and warts (OR=2.07, P =0.012). In contrast, dermographism was not significantly associated with a self-reported history of asthma or allergic rhinitis or other diagnosed skin disorders. Regarding other patient-reported outcomes (Table 2), dermographism was only significantly associated with itch (OR=1.20, P =0.005).The high prevalence suggests that dermatologists should not neglect to test relevant patients for dermographism in order to avoid misdiagnosis, especially in patients of younger age and with comorbid conditions such as atopic dermatitis and symptoms of itch. The significant correlation between dermographism and socioeconomic status indicators may be attributable to urbanization, air pollution, and changes in dietary habits. In conclusion, dermographism affects a substantial proportion of Chinese young adults, and is associated with higher socioeconomic status, comorbidities, and symptoms of itch.