The probe is the most delicate part of the ear thermometer. For the main unit, wipe off dirt on the main unit with a soft dry cloth. Never wash the unit or clean with a cleaner containing abrasive, thinner, or benzine. 

For infrared sensor, when it gets dirty, wipe it lightly with a soft dry cloth or a cotton swab. Do not wipe the infrared sensor with a tissue paper or a towel.