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Applied to small pustules.

The ancients sometimes used this term for pimples; at others, for vesicles. Willan and Bateman define Psydracium to be, a small pustule, often irregularly circumscribed, producing but a slight elevation of the cuticle, and terminating in a laminated scab. Many of the psydracia usually appear together, and become confluent; and, after the discharge of pus, they pour out a thin, watery humour; which frequently forms an irregular incrustation. Frank limits the term to a psoriform eruption, which differs j from itch in not originating from an insect, and is not contagious :-perhaps the lichen. Authors have differed regarding its acceptation.