Eczema is really a catarrhal inflammation of the skin, with the exudate (fluid that escapes) concealed beneath the surface, or appearing on the surface after irritation has occurred. The many varieties are best classified as follows:
(1) Eczema of internal origin, including cases due to morbid agencies produced within the body, cases due to drugs, and possibly reflex cases.
(2) Eczema of external origin, including cases caused by occupation, by climate, or by seborrhea.
Eczema of internal origin almost invariably appears on both sides of the body at once, as on both cheeks, or both arms, or both thighs. Its border shades into the surrounding skin, it is dotted with papules (or heads) filled with fluid, and its surface is clean and not greasy. As it spreads, the symmetry of distribution is lost. Among the morbid agencies producing this variety of eczema are the products of indigestion. Among the drugs producing it is cod liver oil.
