A system for detecting blood in an oral cavity during toothbrushing. The system may include a toothbrush having a sensor that is configured to emit first light at a first wavelength and second light at a second wavelength, receive reflected portions of the first and second light, and generate a first signal indicative of a first intensity of the reflected portion of the first light and a second signal indicative of a second intensity of the reflected portion of the second light. The system may include a processor operably coupled to the sensor, the processor being configured to receive the first and second signals and calculate a ratio of the first intensity to the second intensity to determine whether hemoglobin/blood is present in the oral cavity. The processor may be a part of the toothbrush or a part of a portable electronic device such as a smart phone.