It is essential that the lens of the thermometer is perfectly clean to guarantee the most accurate results. When the lens of an infrared thermometer is dirty (dust, fingerprints, hair...), less infrared radiation passes through the lens. The results are then underestimated.
Check the condition of the lens
Cleaning the lens
Use a cotton swab soaked in 70% alcohol. Gently rub the lens and the metal conduit to remove all traces and dirt.
After cleaning the lens, please wait 30 minutes before measuring again.
*credit to Sylvain of iHealth Labs EU