A method and composition of a photo chromic dye suitable to be applied directly to human skin, and which dye is configured to indicate exposure to UV rays. The composition is configured to change color upon exposure to UVA, UVB and/or UVC rays. The composition can be used with other compositions, such as sunscreen, and be applied to human skin prior to application of the sunscreen, or, formulated with the sunscreen such that when the active ingredients of the sunscreen diminish, the photo chromic dye will change color to generate a visual indicator of this condition.
