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Since 2009, the imiquimod (IMQ)-induced mice model has been extensively adopted as a model of human plaque psoriasis to investigate the mechanisms of psoriatic pathogenesis and to verify the effective of anti-psoriatic drugs [1]. However, the side effects and the mechanism of IMQ-induced weight loss have not been investigated. Recently, we focused on some of those issues in an article which claimed that IMQ induced weight loss and decreased food intake of C57BL/6J mice in the model of generalized pustular psoriasis [2]. The difference of the two mice model between the generalized pustular psoriasis and the plaque psoriasis is the time taken to induce by IMQ. The former is induced for 4 consecutive days, while the latter is induced for 7 consecutive days. Therefore, we were interested in whether IMQ caused weight loss and the mechanism behind plaque psoriasis in the mice model. The male BALB/mice (6–8 weeks of age) were purchased from the Center of Laboratory Animals of Southern Medical University (Guangzhou, China). The mice were randomly divided into two groups of 5-6 each. After 1 week of adaptive feeding, the back hair (1.5×1.0 cm) of the mice was shaved. After 2 days, the two groups of mice were treated topically with vehicle (Vaseline, Lierkang Medical Technology Co., Ltd., Shandong, China; 62.5 mg per mouse) or vehicle and IMQ cream (Ming Xin Pharmaceutical Co. Ltd., Sichuan, China; 62.5 mg per mouse) on their shaved back skin for 7 consecutive days. The psoriasis area and severity index (PASI) scores were monitored to confirm the successful establishment of plaque psoriasis. An objective scoring system was developed based on the clinical PASI to score the severity of mice skin lesion. The scaling, thickening and erythema was scored on a scale from 0 to 4 (0 represented none; 1 represented slight; 2 represented moderate; 3 represented marked; 4 represented very marked). The cumulative scores (scaling plus thickening plus erythema) served as a measure of the severity of lesions (scale 0–12). The single-blind way was used for the PASI scores. Mice on the 2nd day after IMQ induction exhibited signs of plaque psoriasis-like lesion began to appear such as scaling, thickening, erythema and the severity of lesion raised over time (Figure 1A-D). In contrast, the mice treated topically with Vaseline displayed no scaling, thickening or erythema. Those results were consistent with previous study [1] and it suggested that the mice model of plaque psoriasis was successfully established. Subsequently, we investigated whether IMQ caused weight loss of mice in the model of plaque psoriasis. Mice were weighed by electronic scale from the 1st day to the 7th day. Results show (Figure 2A) IMQ caused weight loss of BALB/c mice from the 2nd day to the 7th day. As diet is the determining factor affecting weight, the amount of food and water intake of mice was weighed throughout the trial (We changed fresh food and water, then weigh them to calculate intake at 9 am every day). There was a reduction of food intake caused by IMQ from the 1st day to the 4th day, v-shaped, and this was most evident on the 2nd day (Figure 2B). The food intake of mice induced by IMQ tended to increase compared to the control group *Corresponding author: Wanqun Chen, Department of Gastroenterology, Chongqing Hospital of Traditional Chinese Medicine, 6 panxi branch road, Chongqing 400021, China. Tel: +86023-67063949. Email: [email protected] Jinwei Zhang, Department of Dermatology and Cosmetology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, China Jinwei Zhang, College of the Second Clinical Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China Xiaojun Yang, Hong Qiu, Wanqun Chen, Department of Gastroenterology, Chongqing Hospital of Traditional Chinese Medicine, Chongqing 400021, China #These authors have contributed equally to this work. Jinwei Zhang#, Xiaojun Yang#, Hong Qiu, Wanqun Chen* Weight loss may be unrelated to dietary intake in the imiquimod-induced plaque psoriasis mice model Letter to the Editor