One of the simplest rubefacients is mere friction. This may be made either with the hand, or more effectually still, with a rough cloth or a flesh-brush. Friction also greatly aids the action of many of the slighter rubefacients.

Rubefacients may be used for their action upon the skin itself to relieve itching. They may also be used for their effect on deeper-seated structures.

Friction, with firm pressure, is used in shampooing. Upward friction in the limbs will diminish the tension in dropsy, by removing part of the fluid from them. It also aids the circulation of the lymph, and by accelerating the passage of the products of muscular waste from the muscles themselves into the general circulation, it removes to a great extent the sense of fatigue after over-exertion (p. 131). When applied along the back it soothes conditions of nervous excitement, and tends to produce sleep. Friction, along with stimulating liniments, applied to the joints after active inflammation has subsided in them, tends to remove the swelling and to restore their function.

Neuralgic pains are frequently relieved by the application of rubefacients such as ammonia, chloroform applied by a watch-glass, or a mustard-plaster to the painful spot.

Conditions of nervous debility are sometimes benefited by mustard liniment applied over the spine, and a mustard-plaster to the nape of the neck is sometimes useful in nervous irritability with sleeplessness. In addition to the action which the mustard has on the vessels, it produces a sharp pain, so that it is employed also to rouse persons suffering from narcotic poisoning, or from coma.

Mustard-leaves or iodine liniment applied over consolidated parts of the lung tend to cause absorption of inflammatory products, and are used for this purpose in cases of effusion into the pleura or pericardium, of chronic consolidation remaining after an attack of pleurisy or pneumonia, or in commencing phthisis.