Using infrared thermometers

My wife posed this question to me here at 2:02 AM in the morning. I purchased a Braun thermoscan 6022 digital ear thermometer and love it , due to it's ease of use as well as it's quick reading time. When I went to the pediatric doctor they told me to subtract a degree when using this method. I thought the temperature was what it was. After doing research I found out that there are many variables to this rule," Due you add, subtract, or go on the reading the instrument provides. I know it depends if the child is laying on the right ear you should take the temp in the left because of the heat generated due to the ear being closed off ect. But is there a general rule to using infrared type thermometers? Adding or subtracting a degree? Thanks in advance for the input.