Abstract: A flexible heat pad for heat transfer to a person's limb. The pad consists of a fabric (preferably cotton) envelope enclosing a load of cereal grains, preferably oats. Preferably, the water content of the oat is precisely monitored to remain within the 9 to 14% range by weight of the oat total weight. The quantity of oat grains inside the cotton envelope must be such as to provide even oat distribution within the cotton envelope enclosure, after deformation, whereby localized grainless pockets within the pad enclosure are substantially prevented. The pad is pre-heated for about two minutes inside a micro-wave oven, at full power setting, before use. Thermal inertia of the oat thereafter allows continuous heat diffusion to the limb for about half an hour. The pad may alternately be put into the freezer from at least four to six hours, to thereafter diffuse cold to the swollen limb part of a mammal.