Most snake venoms

"Most snake venoms, and for that matter many other animal venoms, result in tissue inflammation at the site of a bite," says Tamilarasu Kadhiravan, a professor of medicine at the Jawaharlal Institute of Postgraduate Medical Education and Research in Puducherry, India. "Venom-induced inflammation is accompanied by an increase in skin temperature, which is seen as hotspots on infrared images."