Mercury thermometers are the device that many people still think of when they picture a traditional thermometer.
They’re made up of a glass tube with a line of mercury in the centre that moves up or down to show you your temperature.
Digital thermometers are a more recent invention, but they’re far more accurate and are much quicker to use.
We would always recommend using a digital thermometer over a mercury thermometer when taking someone’s temperature.
Mercury thermometers can be more likely to break, causing a risk of injury from glass splinters or exposure to mercury, which is highly poisonous.