Feeling the Burn: Phototoxicity and Photoallergy.

An interaction between light's radiation and certain exogenous and endogenous substances can lead to the development of photoallergic and/or phototoxic dermatoses. Clinically, reactions may range from acute and self-limited to chronic and recurrent. Delays in diagnosis are not uncommon due to complex clinical presentations, broad differentials, and limited number of specialists who perform phototesting. Therefore, a critical understanding of these dermatoses is essential for accurate diagnosis and appropriate management. The epidemiology, light sources, mechanisms, clinical presentations, evaluation protocols, common culprits, treatments, key challenges, and future directions related to photoallergy and phototoxicity are reviewed herein.