[Prurigo diseases].

The term "prurigo" is universally used in dermatology. But, up to now, no definition of this term has been generally accepted. The "classic" description of the "urticarial papules" as the primary skin eruptions of prurigo is not correct, for these papules do not show any momentary edema but a persistent cellular infiltration. In the past, some authors already pointed out that the histologic structure of such papules looks very much like that of the characteristic papulovesicles in eczema--especially those in atopic dermatitis. The various forms of the prurigo nodes secondarily develop in case of the coincidence of three main factors: (1) the particular cutaneous response to repeated irritation (especially in autosomally dominant ichthyosis simplex), (2) reduced threshold for or constitutional disposition to pruritus (especially in atopy), and (3) internal (e.g. intestinal disorders) or external (e.g. insect bites) triggers. Probably none of the prurigo diseases represents a nosologic entity.