4-Hydroxybenzothiazole (4-HBT) is a molecular constituent of pheomelanin-a polymeric skin centered pigment which acts as a natural photoprotector against harmful solar-UV radiation. Its molecular structure is therefore required to sustain a degree of photostability upon electronic excitation with UV irradiation. Despite its function as a protector against UV, pheomelanin is known to be less photostable than that of its close derivative eumelanin-a dark skin centered pigment. The 4-HBT subunit has long being attributed as a key contributor to the lack of photostability of pheomelanin-a hypothesis which we aim to test in this paper. Using high-level multireference computational methods, coupled with on-the-fly surface-hopping molecular dynamics, we find excited state reaction paths that show potential detriment to 4-HBT, leading to phototoxic radicals and products that are distinct from the original ground state molecule. Such radicals and photoproducts include those formed by classic πσ* photodissociations, intramolecular proton-transfer, and ring-opening reactions. Such reactions shed light on the types of molecular structure that show photodetrimental effects upon UV irradiation, allowing judicious predictions for synthetic analogues that may offer enhanced photoprotection in commercial sunscreens.