Body temperature is a vital parameter to check the temperature of humans and consequently crucial to verify the needs of a patient. In humans, the normal temperature is commonly considered to be 37 ° C, however, this is an approximate value  Fever is a physiological response of the organism, during which the neurons increase the temperature above 37 ° C to trigger a series of defensive processes.
For the detection of the temperature, in addition to individual variability, it must also take into account that the body temperature normally fluctuates throughout the day, with the lowest level in the morning and highest in the evening after 6 p.m . The sites of measurement are: axillary , oral sublingual , rectal and front. In axillary measuring, which is the site most easily accessible, it is essential a correct positioning; oral sublingual measurement , which could be unhygienic, is instead quite simple although it may be affected by respiration. The rectal measurement which is unhygienic and uncomfortable, instead allows a rather accurate result, and finally, the front measurement is non- invasive and hygienic when performed with infrared thermometers and it allows a fairly accurate measurement if each of the operating instructions of such devices is followed. The thermometers are classified in IIa Class according to 93/42/EEC Directive.