So obviously rectal temp Is most accurate however my 9 week old is very petite and I'm extremely hesitant also it's not the best if you have to keep checking temp . She had a high temp after her 2 month vaccinations and we ended up in hospital they advised not to use an in ear thermometer as it's not accurate under 6 months but to instead use an under arm digital . The problem I have with that is last night again she was very warm more so her head that say her torso . The in ear said 38.1 and the under arm was saying 37 which is a huge difference and the difference between treating a temp and not ... I'm inclined to believe the in ear as this morning she isn't hit at all and temp seems to have returned to normal