One should only look at this chapter if fever is the only symptom (if there are other symptoms consider those first)

Measuring Fever

• Body temperature should be measured in the mouth (be careful in children less than five years some children may bite the thermometer), ear or armpit.
• Don’t take an oral temperature right after eating or drinking something; it will affect the results.
• The rectum is also accurate but one needs to be careful when using devices to prevent any damage in the rectum (please note: use lubrication, such as petroleum jelly to ease insertion), use from birth to three years.
• Using a thermometer under the armpit is not always accurate and should be used only for general screening, this procedure is often used to prevent the spreading of germs to others.
• Forehead thermometers have shown to be inaccurate because they measure the skin temperature rather than the core temperature.
• Tympanic (ear) thermometers can be difficult to use on babies and are often inaccurate because their ear canals are so small, ideal to use on older children and adults.
• Make sure excess earwax isn’t built up before using this product, as it can cause less accurate results.
• Wash your thermometer before and after use with cold water, then rubbing alcohol. Rinse thoroughly to remove the alcohol.

• Source: NICE. Feverish illness in children: assessment and initial management in children younger than five years, 2013