An optical analysis of saliva or a fluid-saliva mix obtained during or after an oral care action is performed in order to check whether the saliva or fluid-saliva mix contains blood, which allows for determining whether or not a person may suffer from gingivitis or another condition affecting gum health. In particular, light received from a representative sample (23) containing saliva is detected and analyzed. The analysis involves determination of measurement values of light received by a light receiving unit (25) for one or more main wavelengths of the light and one or more auxiliary wavelengths of the light. Advantageously, the main wavelength(s) is/are associated with high hemoglobin absorption and the auxiliary wavelength(s) is/are associated with low hemoglobin absorption. A measurement value at an auxiliary wavelength is used for correcting a measurement value at as main wavelength for background influences.
