Octyldimethyl para-aminobenzoic acid (OD-PABA) is an organic ultraviolet (UV) filter chemical that is found in many cosmetic products, including lip balms and sunscreens, to protect the skin from sun damage. When exposed to UV light, OD-PABA produces photoproducts which we are examining the cellular toxicity to determine what levels can be deemed safe for human exposure. In conducting this research, we placed a prepared solution of OD-PABA in a solar simulator to create the effect of sunlight exposure, which in turn generates the photoproducts. We then used high performance liquid chromatography (HPLC) to separate out the photoproducts. Individual photoproducts were then tested for their cellular toxicities. We are currently focusing on one photoproduct which we call “P4” for product 4, which is the fourth product that elutes from the HPLC. We have tested a range of concentrations of P4 from 0.001 mM to 2 mM, and our data so far have suggested that concentrations of 0.25 mM and higher are significantly toxic to mammalian cells. Ongoing research is focused on further understanding the relationship between P4 concentration and cellular toxicity. These methods can also be applied to other photoproducts of OD-PABA to determine their respective cellular toxicities.