Abstract
Photodynamic therapy (PDT) is a minimally invasive therapy that utilizes singlet oxygen produced by
irradiating a tumor-accumulating photosensitizer with excitation light. One of the challenges of PDT is
photosensitivity caused by residual photosensitive drugs in the skin. Exposure of skin with residual photosensitive
drugs to sunlight causes photosensitivity such as erythema, blistering, and hyperpigmentation
of the skin. The light-blocking period established to prevent photosensitivity does not indicate the duration
of hospitalization, but inpatient observation is often performed. Decreased patient QOL due to light
shielding, such as progression of amnesia during light shielding hospitalization in elderly patients, is a
problem. This article reviews the status of photosensitivity and a quantitative monitoring system for
drug concentrations in skin tissues to obtain scientific evidence for discharge timing and home management
in PDT.
