General method of eruption. Successive advancing lesions. Definition.
Causes: usual factors and special susceptibility.
This term, standing for what boils out, has long been applied to
vesicular eruptions on the skin, but inasmuch as the inflammation rarely
stops short with vesiculation, but usually in part at least goes on to
more advanced lesions, it must be held to include in many cases
erythema, papules, vesicles, pustules, crusts, desquamations and
erosions. All of these may coexist or succeed each other in the same
subject, so that considerable latitude must be allowed to the name to
cover all parts and stages of the same attack. Dermatologists have
defined eczema as a non-infectious inflammation of the skin with
multiform manifestations, but recent observations would indicate that it
may at times, at least, be contagious, and micrococci have been found in
the serum of the vesicles, while the very occurrence of pus must
virtually imply the existence of a bacterial infection. Doubtless
different diseases pass under this name in the different genera and
species, and even in the same variety of animals, yet until we learn to
discriminate sharply the one from the other, it is convenient to
consider the whole as a kindred clinical group, if not a pathological
entity.
_Definition._ An acute or more frequently, a chronic inflammation of the
skin and sometimes of the mucosæ, characterized by itching, erythema,
papules, vesicles, serous or sero-purulent exudation with squama or
crusts and loss of hair, and usually largely due to an internal cause.
The exudative condition has suggested a catarrh of the skin.
_Causes._ These are the usual causes of skin disease, local and general,
together with a special susceptibility, under which, what are ordinary
irritants produce this characteristic disease. Many local irritants can
produce eczema, but again it is often the case that these factors will
operate on a given susceptible subject while on another they are without
much effect. This susceptibility is called a “dartrous diathesis” by the
French writers, while most English and American writers are willing
rather to find the hidden cause or causes in the disorder of internal
organs (digestive, hepatic, urinary, generative, hæmatic, trophic,
infective, plethoric, atonic).