A patch having an infrared (IR) target is placed proximate to the surface of a mammal. The patch may include an insulator for protecting the target from exterior, ambient IR and may include bar codes or other indicia uniquely associated with either the patch or the mammal. The patch may also include a bio-reactive agent for indicating characteristics such as the pH of the mammal's skin. The patch may also include a thermometer for sensing the level of IR radiation from the IR target and may include a display of the temperature associated with such a level. The patch may also include a transmitter for wirelessly communicating information about such level to a remote location. A method of using the patch is also disclosed.