Indicia readers may be configured with two illumination light sources: a primary light source for illuminating primary indicia (e.g., a barcode) and a secondary ultraviolet (UV) light source for revealing secondary indicia (e.g., UV fluorescent watermarks) that are used to protect against counterfeit and fraud. Ultraviolet light can be harmful. The present invention embraces methods and a device for controlling the secondary UV light source to limit UV exposure. When an exposure risks is detected, the UV light source is deactivated.