The characteristic features of this disease are the accumulation of scales in raised patches and thickening of the underlying skin. In the horse psoriasis mostly prevails in the heavier breeds, and especially among animals fed up for exhibition. It is chiefly limited to the neck close to the mane, the inner aspects of the ears, and over the tail. The affection commences in circumscribed spots, which gradually extend and unite to form large scaly patches. In the bends of the joints it is generally the case that cracks appear in the skin from which discharge issues, and from the constant movement in the part the fissures do not readily heal, and the irritation which exists sometimes causes general stiffness of the limb and lameness.

The treatment to be employed is chiefly local. Carbolized oil, or zinc ointment, or in some cases iodine ointment, according to the stage of the disease, may be employed; but it is well recognized that, although the affection may be subdued and kept under for a time, it is extremely difficult to cure. Overfeeding, want of exercise, and dirty stables are common causes of its recurrence when once subdued.