Clinical Classification of Itch: a Position Paper of the International Forum for the Study of Itch

TLDR

Chronic itch is a common, distressing symptom arising from diverse skin and systemic conditions, yet no clinically based classification exists to guide diagnosis and care. The authors propose a classification based on clinical signs that separates pruritic diseases with or without primary or secondary skin lesions to serve as a diagnostic pathway and improve patient care. The system groups pruritus into three categories—on diseased skin, on non‑diseased skin, and with severe secondary scratch lesions—and further classifies underlying diseases into dermatological, systemic, neurological/psychiatric, mixed, or unknown causes. This is the first version of a clinical classification developed by the International Forum for the Study of Itch.

Abstract

Chronic itch is a common and distressing symptom that arises from a variety of skin conditions and systemic diseases. Despite this, there is no clinically based classification of pruritic diseases to assist in the diagnosis and cost-effective medical care of patients with pruritus. The proposed classification focuses on clinical signs and distinguishes between diseases with and without primary or secondary skin lesions. Three groups of conditions are proposed: pruritus on diseased (inflamed) skin (group I), pruritus on non-diseased (non-inflamed) skin (group II), and pruritus presenting with severe chronic secondary scratch lesions, such as prurigo nodularis (group III). The next part classifies the underlying diseases according to different categories: dermatological diseases, systemic diseases including diseases of pregnancy and drug-induced pruritus, neurological and psychiatric diseases. In some patients more than one cause may account for pruritus (category "mixed") while in others no underlying disease can be identified (category "others"). This is the first version of a clinical classification worked out by the members of the International Forum for the Study of Itch. It is intended to serve as a diagnostic route for better evaluation of patients with chronic pruritus and aims to improve patients' care.