Objective:To investigate serum lipidomic profiles in patients with chronic actinic dermatitis (CAD), and to search for biomarkers of CAD.Methods:A retrospective analysis was conducted. Serum samples were collected from 46 patients with CAD and 16 age- and gender-matched healthy controls in the Guangzhou Institute of Dermatology from April 2011 to December 2021. Changes in serum lipid composition and expression were assessed by liquid chromatography-mass spectrometry. Principal component analysis, partial least squares discriminant analysis, and orthogonal partial least squares discriminant analysis were performed to screen differential biomarkers, and receiver operating characteristic (ROC) curve analysis was conducted to screen diagnostic markers. Comparisons of the age and gender distribution between groups were performed using t test and chi-square test, respectively. Results:The 46 CAD patients were aged from 30 to 84 (60.39 ± 10.52) years, including 41 males and 5 females; the 16 healthy controls were aged from 50 to 89 (59.81 ± 10.72) years, including 14 males and 2 females; there were no significant differences in the age or gender distribution between the two groups (age: t = 0.19, P = 0.853; gender: χ2 = 0.03, P = 0.859). Totally, 4 136 lipid molecules belonging to 40 subclasses were identified in the serum samples from CAD patients as well as healthy controls. Twenty-two differential lipid molecules were identified between the CAD patients and healthy controls, belonging to 9 subclasses (triglycerides, sphingomyelin, phosphatidylserine, phosphatidylethanolamine, monofatty acid glycerides, lysophosphatidylcholine, hexose ceramide, diglycerides, and cardiolipin). When the combinations of triglycerides (37.7e) and Na, those of monoglycerides (22.3) and NH 4, or those of phosphatidylserine (18.0_18.1) and H served as diagnostic markers separately, the areas under the ROC curve (AUCs) were all > 0.8, and the AUCs of 16 differential lipid molecules were all > 0.7. Conclusion:The serum lipid composition differed between healthy controls and CAD patients, and the combinations of triglycerides (37.7e) and Na, those of monoglycerides (22.3) and NH 4, and those of phosphatidylserine (18.0_18.1) and H may be promising biomarkers for the diagnosis of CAD.