What initial investigations should I consider for a patient presenting with a suspected photosensitivity reaction?

Initial investigations for a patient presenting with a suspected photosensitivity reaction should begin with a detailed clinical history and examination to identify potential causative agents, including recent drug exposures and sun exposure patterns ¹. Blood tests may be considered to exclude systemic causes or associated autoimmune conditions, such as antinuclear antibodies (ANA) and other relevant serologies ¹. Phototesting, including photopatch testing and phototolerance testing, can help confirm photosensitivity and identify specific wavelengths causing the reaction ¹. Additionally, skin biopsy may be warranted in uncertain cases to differentiate photosensitivity from other photodermatoses or dermatological conditions ¹. From a pharmaceutical chemistry perspective, understanding the patient's medication history is crucial, as drug-initiated photosensitivity involves photochemical reactions triggered by certain drugs, which can guide targeted investigations and management (Rácz Á and Tóth, 2015). Therefore, integrating clinical, immunological, and photobiological assessments provides a comprehensive approach to initial investigations in suspected photosensitivity reactions ¹; (Rácz Á and Tóth, 2015).