A dispenser for dispensing a product, the dispenser comprising a base unit (2) into which a refill (1) containing the product is removably insertable in a fixed position. The refill has a taggant ink (12) on part of its external surface. The base has a light source (13) to illuminate the ink. The light source has a first wavelength and the ink is arranged to cause the ink to emit light at a second different wavelength. A sensor (14) receives light emitted by the ink upon illumination by the light source. A control circuit receives signal indicative of the wavelength of the detected light from the sensor, compares it with stored data, and prevents operation of a dispensing mechanism unless the refill is authentic.