Diaphoretics, known also as sudorifics, are medicinal substances capable of producing perspiration, or an increase of the cutaneous discharge, which may be occasioned by the mere drinking of a large quantity of fluid, provided the temperature of the system be kept up. The determination of blood to the cutaneous vessels by a warm temperature or exercise will produce diaphoresis, and the action of nauseating agents, by relaxing the orifices of the cutaneous vessels, and also stimulants, by exciting such vessels to increased secretion, will have the same effect.

The external application of heat, friction, etc., stimulates the cutaneous capillaries and causes an increased secretion.

Diaphoresis may also be excited by medicines which enter the circulation and stimulate the cutaneous vessels by contact, such as the mercurials and sulphur; also by medicines which act on the surface sympathetically, through the medium of the stomach, as cold drinks, etc.

Diaphoresis may also be produced by increasing the general action of the vascular system, by such means as violent exercise, the warm bath, and by the use of alcohol, ammonia, guaiacum, etc.; it may also be produced by the use of agents, capable of relaxing the morbidly constricted mouths of the perspiratory vessels, such as the antimonials, saline diaphoretics, and by the operation of venesection.

Nauseating diaphoretics are employed to produce a powerful relaxing action in inflammatory cases not complicated with gastric irritability, and for such effects the emetics ipecacuanha and the preparations of antimony are administered.

Refrigerant diaphoretics are employed to produce a gentle relaxing effect in allaying febrile excitement and reducing the temperature of the body.

Stimulating diaphoretics are employed in rheumatic and pulmonary affections, after vascular excitement has been reduced, and where the surface is cool, being contraindicated in a high degree of inflammation. For such effects, the diffusible stimulants, aromatic substances, and such narcotics as opium and camphor are administered. During the administration of diaphoretics, the patient should be confined to bed, and when diaphoresis is excited, it should not be suddenly checked. Venesection is generally resorted to when there is great arterial excitement with undue heat of skin, before the attempt is made to administer diaphoretics.

Belonging to the class of diaphoretics are such agents as Dover's powder, guaiac, spirits of mindererus, nitrate of potassa, sweet spirit of nitre, etc., etc.