ERUPTION, a term applied to a local disturbance in the skin characterized by the for mation of redne.ss or scaliness, blistering or pustulation. In one class of affections, known as the eruptive fevers, a characteristic form of skin-eruption is diagnostic. Thus the fine red rash of scarlet fever, the bluish red rash of measles, the irregular rash of chickenpox and the pustulate rash of smallpox are readily recog nized. The popular notion that an eruption is an indication of something evil within the body finding its way out belongs to the medimval days of superstition and ignorance, when disease was regarded as an evil spirit to be exorcised, and gave notice of its evacuation by means of an eruption on the skin. At the present time we know that most eruptions are either of purely local occurrcnce, due to localized irritants, as in the case of pimples, boils, etc., or that they represent a disturbance of the nerve-centres, whose end-filaments are distributed to the epi thelial structures of the body. Thus in measles, not only the skin, but also the mucous mem branes of the respiratony tract are affected, the poison affecting the nerve-structures being evi denced by nerve-irritation at the periphery of the body. The popular idea that it is necessary
to bring an eruption out in acute infectious diseases such as measles and scarlet fever is trustworthy, but an interpretation is frequently given to it that is not sound. The presence of an eruption on the surface of the body in these affections is an indication of the protective ener gies of the human organism in its fight with the infection and poisoning. The inability of the body to counteract the poison of the disease may prevent the development of the eruption, and thus its bringing out, being the sign of the body's ability successfully to cope with the poison, is the warrant for the popular idea of the efficiency of the eruption. Many drugs locally applied, or taken internally, cause the formation of eruptions. These eruptions may be due to purely nervous influences, or they may be of local origin. Drug-eruptions following the use of the iodides and bromides are of this latter character. As the drug is eliminated through the skin, its passage there causes local irritation and the formation of an eruption. See Dow:rills; MF.ASLES ; SKIN AND SKIN DIS EASES.