Abstract: A radiation indicator device for use in indicating exposure to ultraviolet-B radiation. The device includes a radiation sensitive mixture which is selectively responsive to ultraviolet radiation having a wavelength substantially within or shorter than the range of wavelengths of ultraviolet-B radiation. The radiation sensitive mixture includes an organic halogen constituent capable of producing at least one acidic product upon exposure to ultraviolet radiation and an indicator constituent capable of producing a change in color in response to a change in concentration of the acidic product. The radiation sensitive mixture has a first color representing a relatively low concentration of the acidic product and has a second color representing a relatively high concentration of the acidic product. The first color is visually distinguishable from the second color.