This tests for reflex sweating by elevating general body temperature. Signals then pass to the hypothalamus and travel via the intermediolateral cell column, sympathetic chain and postganglionic sudomotor nerves to the sweat glands. A material which changes colour when mixed with sweat, such as alizarin red, corn starch or sodium carbonate is applied to the skin of the unclothed subject who is then placed in a cabinet or room with heaters which raise the air temperature to 44 to 50C with a constant humidity. Normally, when the temperature rises by 1C above baseline (temperature to above 38C), uniform sweating is seen over the entire body, with characteristic areas of the body displaying either increased or decreased amounts of sweat production. This can then be quantified by photographing the body areas and digitizing the change in colour or appearance of the test powder.