This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Emollients are substances which soften and. relax, while Demulcents are substances which protect and soothe the parts to which they are applied.
Many substances exercise both of these actions, and so no very sharp line of distinction is drawn between them. Emollients, however, are more generally spoken of in relation to their application to the skin, and demulcents to the mucous membranes.
Cotton-wool (for external use only). Figs.
Moist warmth - bathing with warm water, hot sponge, hot fomentations, steam.
Poultices made of substances which retain heat and moisture - bran, bread, figs, flour, linseed-meal, oatmeal, etc.
Paraffin - petrolatum, vaseline, and unguentum petrolei.
Soap and other liniments.
The Action of Demulcents is chiefly mechanical. They form a smooth, soft coating to an inflamed mucous membrane, or to a skin deprived of its epidermis, and they thus protect the surface from external irritation, and allow the process of repair to go on. They are used externally in cases of irritating skin diseases, where the epidermis from one cause or another has been broken or removed, as by friction, exposure to cold, etc. Internally they are employed when the mucous membranes have been irritated, as, for example, in the after-treatment of cases of irritant poisoning.
Mucilaginous substances are also used to relieve pain and irritation in the throat, and to lessen the irritable cough which frequently depends on congestion of the pharynx and upper parts of the respiratory passages.
Such substances as figs, prunes, and even cabbage, are employed to protect the intestines from injury by hard and pointed substances which have been accidentally swallowed. They do this by leaving a bulky indigestible residue in which the pointed article becomes embedded, and thus passes along the intestine without lacerating it.
The Action of Emollients is to relieve the tension and pain in inflamed parts; warmth and moisture do this by dilating the collateral blood-vessels in the manner already described (p. 342). They also relax the tissues themselves and lessen the pressure upon the nerves of the part.
Fatty emollients soften the skin and thus render it softer and more flexible. These emollients also aid the immediate effect of friction upon the skin, enabling it to be applied with greater advantage, and to act on the more deeply-seated tissues, as, for example, in cases of stiffness in joints.
Warmth and moisture are almost invariably used to relieve spasm and the pain attending it, as well as to relieve pain in all cases of inflammation, whether superficial or deep-seated, and they relieve so much that, with many people, the connection between pain and poultice has come to be a household word. When poultices are intended to act directly on the part to which they are applied, the linseed, bran, or bread should be applied to the skin with nothing between, or at most with only a thin piece of muslin, but when intended to act on deep-seated organs, a considerable thickness of flannel should be interposed, so that the heat may come gradually through, and allow an excessively hot poultice to be applied without burning the skin.
In cases of disease of the respiratory passages the warmth is usually applied by means of inhalation.
Fatty emollients, by softening the skin or mucous membranes, such as those of the lips, prevent them from cracking, and are used by persons with a delicate skin to prevent cracks forming on exposure to cold.
They are also used to prevent friction between surfaces of skin constantly in contact, as between the nates and inner joints in children, and to prevent bed-sores.