Abstract: Clothing and an associated method of use for modifying body temperature by transdermally modifying blood temperature comprising having a thermal device retained within at least one garment pocket substantially overlying at least one major blood vessel so as to increase the temperature gradient of said blood across said at least one major blood vessel so as to use said blood to act as a heat transfer fluid, said garment being fitted so as to press said pocket and said thermal device closely to the skin of the wearer and said pocket being arranged to be substantially aligned along the length of said major circulatory vessel while minimizing overlap across tissue surrounding said major blood vessel.