A thermal device comprising a garment (42A) that may be placed against at least a part of the body (10), the garment (42A) defining at least one enclosed compartment (48, 50) defined between an inner wall (65) and an outer wall (66), and an inlet (21) whereby liquid may be introduced into each such enclosed compartment (48, 50). Each enclosed compartment (48, 50) contains dry material (30) comprising water-soluble chemical compounds that dissolve endothermically or exothermically, and also a compressed sponge (62). There may also be an air bleed valve (64) to bleed any air out of the compartment (48, 50) when water is introduced. The device enables a patient's body to be cooled or heated in emergency, needing only addition of water, and incorporating no toxic or hazardous materials.
