noun. Sensitivity or responsiveness to light.

noun. An abnormally heightened response, especially of the skin, to sunlight or ultraviolet radiation, caused by certain disorders or chemicals and characterized by a toxic or allergic reaction.

noun. sensitivity to light, especially a heightened response to light

noun. sensitivity to the action of radiant energy

"Some chemotherapy drugs cause a condition called photosensitivity, which refers to an increased sensitivity to the sun."

sensibility  sensitiveness  sensitivity