To me, the best way is under the arm, but the doctor will always say "Well we don't know what his ACTUAL temperature is." What you need to do if you want to take a temp this way (auxiliary temp) is remember that the child's actual temp will be higher - you have to add a degree or two to the auxiliary temp.
But instead of memorizing the difference, here is what I do. I take my child's temp, under the arm, several times over a few weeks, to see what his average temp is when he isn't sick. Then I write that down, and when he gets sick and I take his temp, I pay attention to how much higher it is than his normal auxiliary temp. Then if it seems pretty high, i know the doc will take an accurate temp when I take him in anyway.
Good luck! I tried hte forehead one and the ear one too, btw, and couldn't get consistent results - I'd take the temp twice in a row and get 2 very different temps!
at 8:50 PM on Jan. 3, 2011