The Erythemal Response Spectrum is a scientific expression that describes the skin sensitivity to the ultraviolet radiation. A long exposure to UV radiation causes skin erythema once a threshold dose has been exceeded. We present a sensor based on a liquid crystalline mixture, containing dye, that absorbs photons at UV wavelength and emits them in the visible range of the electromagnetic spectrum. In particular the absorption spectrum of the mixture can be modulated to be similar to the Erythemal Response Spectrum. This system presents several innovative features: the absorption range of the mixture can be varied to be sensitive to different wavelengths, the luminescence intensity can be tuned, the system can be implemented on flexible devices, providing the possibility to create a dosimeter for ultraviolet radiation.