MODEL RELEASED. Measuring body temperature. Strip thermometer being used to measure the temperature of the forehead of a 4-month-old baby girl. There are liquid crystals in the strip that change shape and reflect light with changes in temperature. The different areas of the strip contain crystals that are designed to respond at different temperatures. The strip thermometer shows that the baby girl's skin temperature is about 38 degrees Celsius. This indicates that she may have a slight fever, where her core (body) temperature is slightly raised. A slight fever is mostly harmless and helps the body to fight infection. However, a severe fever in a young baby requires medical attention.