Exposure to the ultraviolet (UV) radiation contained in sunlight has both beneficial and detrimental health effects. Assessing how much UV one has received, particularly if it is recent exposures, is important but difficult. Cumulative (lifelong) UV exposure can be routinely assessed by questionnaire or through silicone hand casts. In contrast, there is as yet no reliable method for quantifying the biological effect of recent episodes of UV exposure. The ability of UV to suppress adaptive immune responses is thought to be central to both its beneficial (protection from autoimmunity) and detrimental (carcinogenic) effects. We therefore hypothesised that there may be a UV-induced molecule that could act as a biomarker of immune-suppressive UV. Previous work revealed a key role for lipids particularly platelet-activating factor in mediating UV-induced immune suppression. To assess whether UV was altering other lipids, we adopted a discovery lipidomics approach to identify novel biomarkers in plasma. Mice were exposed to an immune suppressive (8,000 mJ/cm2) dose of solar-simulated UV. Blood was collected 24 hours later and the extracted plasma lipids were analysed by discovery mass spectrometry. Analysis of the plasma identified 7 lipids with increased levels in UV-irradiated mice. Notably, these lipids were not murine-specific with all 7 lipids also being identified in normal human plasma. This study has uncovered several lipid biomarkers of UV exposure in the plasma. While more is needed to determine the correlation between lipid levels and immune suppression, this is an important first step in developing a clinically important tool in measuring the effects of UV on the immune system.