PSORIASIS as commonly met with is not difficult to differentiate. The numer ous, variously-sized, sharply-defined scaly patches, of general distribution, of psori asis make this disease sufficiently char acteristic. The face and hands are rarely involved, or only to a slight extent, at least, in psoriasis, while these regions are favorite sites for eczema. The psoriasic eruption often is seen most markedly on the extensors of the arms and legs, espe cially about the elbows and knees; ec zema is more common in the flexures. Psoriasis is usually markedly scaly, ec zema rarely so. In occasional instances psoriasis is limited to the scalp, appear ing here as several or numerous vari ously-sized scaly areas, resembling squamous eczema of this part. The same differential characters can be here recognized, if the case is studied, as when seated upon other parts. Moreover, a careful examination will usually disclose the presence of several small or mod erately sized characteristic psoriasic patches on the limbs, especially about the elbows and knees. Eczema of the scaly type is -usually seated upon one region, is rarely generalized in its dis tribution, and the area or areas are rarely sharply defined. Itchin,g is the rule in eczema and is often absent or slight in psoriasis. In many cases of chronic scaly eczema there is often a history of gummy oozing which does not obtain in psoriasis. The eruption produced in the parasitic disease scabies and pediculosis is essen tially eczematous in many of its char acters, but is usually multiform, consist ing of papules and pustules, the latter often being large in size. The distribu
tion of the eruption in these parasitic diseases will often be sufficiently char acteristic, and suspicion may be con firmed by the finding of the pediculus in pediculosis or by the burrow in scabies. Seborrhcea at times bears close resem blance to a mild eczema, more especially as it occurs on the scalp. The sehor rhceic disease is, however, rarely inflam matory, except accidentally so; the scales are greasy, and there is lack- of infiltra tion and thickening.
SYCOSIS.—Eczema of the bearded face may be mistaken for sycosis, but this latter disease is essentially one of the hair-follicles — folliculitis barbm — and limited to the hairy region of the face, and is rarely itchy. Eczema, on the other hand, is seldom limited to this region, but extends on to the non-hairy parts of the face, is not follicular, and is very itchy. Ringworm can scarcely be confounded with eczema, as eczema is seldom sharply defined, rarely ring shaped, but is diffused, with no tendency to clear up in the centre. In cases of a doubtful character microscopical exam ination of the scales will be sure to differ entiate.