This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Heat applied to the skin, in the modes treated of under diffusible stimulation (i. 490), cannot be regarded as rubefacient. it acts on the whole system directly, by means of the blood, which conveys everywhere through the body the heat it receives at the surface. But it is sometimes employed with a view simply to the local inflammation it produces, and thus properly falls into the present category.
Rubefaction may be effected either by water not sufficiently hot to vesicate, applied by means of cloths or the douche, or by a stream of hot air, or by a solid body heated. The last is the most convenient method, and has been considerably used in the treatment of chronic rheumatism. A smooth piece of iron, furnished with a handle, having been heated somewhat above 212°, may be applied lightly to the skin, and passed rapidly from point to point, till the desired extent of surface has been covered. The skin is first whitened, but soon becomes red and inflamed; and, by careful manipulation, a rapid rubefaction can thus be obtained, without cauterization, or even vesication. it is obvious that this measure might be applied extensively for the general purposes of the rubefacients; but the chances of injury from unskilful or careless manipulation, and the painful character of the inflammation produced by heat, tend very much to limit its employment.