Thermogram of an infected middle finger, left hand. The image shows the 'heat signature' left behind of the hand of a person experiencing symptoms of Raynaud's against that of a person who is unaffected; ; The hand affected with Raynaud's is on the right, the other hand is unaffected. This image shows the heat pattern left behind once the hands are lifted from the surface.; ; Thermal Infrared is found within the Infrared region on the electromagnetic spectrum.; ; The different colours in the images represent different levels of thermal energy being emitted from the skin's surface. In this image the yellow and orange colours show a high level of thermal energy and the blue and purple a lower level. ; ; Raynaud's phenomenon (also referred to as Raynaud's syndrome or Raynaud's disease) affects the bodily extremities, most commonly the hands and feet. On exposure to cold or stress, the blood vessels at the extremities constrict or narrow restricting the flow of blood, this is called vasoconstriction. When this happens in the hands then the fingers will often change colour becoming very pale as less blood reaches the surface of the skin, this means there is also less radiation of heat from the affected area.
