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 NICE CG183. Blood tests may be considered to exclude systemic causes or associated autoimmune conditions, such as antinuclear antibodies (ANA) and other relevant serologies NICE CG183. Phototesting, including photopatch testing and phototolerance testing, can help confirm photosensitivity and identify specific wavelengths causing the reaction NICE CG183. Additionally, skin biopsy may be warranted in uncertain cases to differentiate photosensitivity from other photodermatoses or dermatological conditions NICE CG183. 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 & Tóth 2015. Therefore, integrating clinical, immunological, and photobiological assessments provides a comprehensive approach to initial investigations in suspected photosensitivity reactions NICE CG183; Rácz Á & Tóth 2015.