Thanks to John Sandham. You have raised some interesting points that I will need to consider.
When I came across the Exergen it made me think of doctors and their stethoscopes. Surely they can be cleaned in the same way? Although how often do doctors clean their stethoscopes? I doubt its after every patient!
The other point is testing. I know that tympanic thermometers can be checked using a portable blackbody to ensure they are within limits. Is there a similar method for the Exergen or Thermofocus?