Irritants, Counter-Irritants. These when applied to the skin cause vascular excitement; are called counter-irritants when used to produce reflex influence on remote parts: (a) Rubefacients (L. rubere, to be red, + facere, to make) - which produce temporary redness and skin congestion; if left on too long, may cause exudation between the cuticle and true skin (vesicants), or may destroy the tissue, forming a slough (escharotics), or may cause muscular atrophy: mustard, capsicum, mezereum, iodine, menthol, ammonia, arnica, volatile oils (turpentine, cajuput, etc.), hot water, friction; (b) Vesicants, Epispastics, Blisters (L. vesica, a blister; Gr.
to draw) - which produce much inflammation of the skin and effusion of serum between the epidermis and derma: cantharides, mezereum, iodine, rhus toxicodendron, glacial acetic acid, volatile oil of mustard, steam, boiling water, ammonia vapor; (c) Pustulants (L. pustulare, to blister) - which cause pustules, and affect isolated parts of the skin, as orifices of sudoriferous glands: croton oil, tartar emetic, silver nitrate; (d) Escharotics, Caustics (Gr.
a scab, scar) - which destroy tissue when applied, by abstracting its water, or by combining with the albumin of the skin, or by corrosive deoxidation of the tissues, thus causing a slough: mineral acids, phenol, chromic acid, lime, potassium and sodium hydroxides, dried alum, silver nitrate, zinc chloride, copper sulphate, corrosive mercuric chloride, mercuric oxide and nitrate, bromine, high heat, electric cautery, boiling water, arsenic trioxide. 42. Styptics, Haemostatics (L. stypticus, contracting; Gr.
to stop, stopping). - These arrest hemorrhage; the former being used locally, the latter internally. Some act mechanically, by closing the mouths of the bleeding vessels with a blood-clot; others contract the vessels, thus checking the blood-flow: (1) acids, alum, collodion, ferric chloride and sulphate, silver nitrate, matico, tannin, lead acetate, zinc sulphate, vegetable astringents, cold (locally), electric cautery; (2) ergot, gallic acid, matico, lead acetate, diluted sulphuric acid, hamamelis, oil of turpentine, heat (locally).
43. Emollients (L. emollire, to soften). - These soften and relax the tissues when applied locally, diminish the tension and pressure on the nerves, dilate the vessels, and protect inflamed surfaces: poultices, fatty oils, lard, spermaceti, glycerin, petroleum, starch, soap liniment, cacao-butter.
44. Demulcents (L. demulcere, to soothe). - These, usually mucilaginous or oleaginous, are intended for soothing parts to which applied, being restricted generally to mucous membranes (internally), and emollients to the skin (externally): acacia, cetraria, starch, flaxseed, licorice, gelatin, honey, althaea, egg-white, tragacanth, olive and other bland oils.
Protectives. These are mechanical coverings to protect various injured parts from air, water, friction, etc.; collodion, plasters, etc.