Abstract: Objective To study the effects of seawater immersion on the inflammatory response and oxygen free radical injury of rats with superficial-thickness scald at early stage. Methods Seventy Wistar rats were divided into healthy control group (HC, n=7), pure scald group (PS, n=21), scald+ fresh water immersion group (SF, n=21), and scald+ seawater immersion group (SS, n=21) according to the random number table. Rats in group HC did not receive any treatment, while 5% total body surface area superficial partial-thickness scald was made on the back of rats in the latter three groups. Rats in group PS lived freely immediately post burn, while wounds on the back of rats in groups SF and SS were immersed into fresh water and seawater, respectively. Serum and full-thickness skin tissue in the center of wounds on the back of 7 rats in groups PS, SF, and SS at post immersion (injury) hour (PIH) 2, 4, and 6 were collected, respectively, while serum and full-thickness skin tissue at the same position of the 7 rats in group HC were collected at PIH 6 of rats in other groups. Morphology of skin tissue was observed with HE staining; tumor necrosis factor-alpha (TNF-α) content in serum and skin tissue was determined by enzyme-linked immunosorbent assay; superoxide dismutase (SOD) content in serum and skin tissue was determined by hydroxylamine method; malondialdehyde content in serum and skin tissue was determined by thiobarbituric acid method. Data were processed with analysis of variance of factorial design, one-way analysis of variance, Welch test, LSD test, and Tamhane test. Results (1) Epidermal cells of skin tissue of rats in group HC arranged in order and continuously, and the dermis tissue and accessory structures were clear and complete. The skin layer and epidermis of wounds of rats in group PS had no significant change, but the edema of epidermis and dermis and infiltration of inflammatory cells enhanced over time at PIH 2, 4, and 6. The horny layer of epidermis of wounds of rats in group SF reduced, and the edema of epidermis and dermis and infiltration of inflammatory cells enhanced over time at PIH 2, 4, and 6; some epidermal cells disintegrated at PIH 6. The horny layer of epidermis of wounds of rats in group SS significantly reduced, along with the increase in disintegration of epidermal cells, the significant enhancement of edema of epidermis and dermis, and infiltration of a large number of inflammatory cells over time at PIH 2, 4, and 6. (2) Compared with (247±27) pg/mL in group HC, the serum content of TNF-α of rats in group PS significantly increased at PIH 2 and 4 [respectively (675±122) and (367±54) pg/mL, P<0.05 or P<0.01] but significantly decreased at PIH 6 [(147±27) pg/mL, P<0.01]; the serum content of TNF-α of rats in group SF significantly decreased at PIH 6 [(90±24) pg/mL, P<0.01]; the serum content of TNF-α of rats in group SS significantly increased at PIH 2, 4, and 6 [respectively (1 646±58), (2 086±114), and (2 951±58) pg/mL, with P values below 0.01]. Compared with (364±123) U/mL in group HC, the serum content of SOD of rats in group PS significantly increased at PIH 2 and 4 [respectively (489±13) and (447±14) U/mL, with P values below 0.05]; the serum content of SOD of rats in group SF significantly decreased at PIH 6 [(282±13) U/mL, P<0.05]; the serum content of SOD of rats in group SS significantly increased at PIH 2 [(461±23) U/mL, P<0.05] but significantly decreased at PIH 4 and 6 [respectively (226±8) and (205±10) U/mL, with P values below 0.01]. Compared with that in group HC, the serum content of malondialdehyde of rats in groups PS, SF, and SS significantly increased at PIH 2, 4, and 6 (with P values below 0.01). (3) Compared with that in group HC, the TNF-α content in wound tissue of rats in groups PS and SS significantly increased at PIH 2, 4, and 6 (P<0.05 or P<0.01), and the TNF-α content in wound tissue of rats in group SF significantly increased at PIH 2 and 4 (with P values below 0.01). Compared with that in group HC, the SOD content in wound tissue of rats in groups PS and SF significantly increased at PIH 2, 4, and 6 (P<0.05 or P<0.01), and the SOD content in wound tissue of rats in group SS significantly increased at PIH 2 and 4 (with P values below 0.01). Compared with that in group HC, the malondialdehyde content in wound tissue of rats in groups PS, SF, and SS significantly increased at PIH 2, 4, and 6 (with P values below 0.01). Conclusions Seawater immersion can enhance the inflammatory response and oxygen free radical injury of wounds and the whole body of rats with superficial partial-thickness scald at early stage.