It’s been hundreds of years since German physician Samuel Haffenreffer first described the sensation of “itch” in 1660, but experts and patients have at last settled on a new definition for pruritus they hope will help facilitate the development of new therapies in future.
The move follows concerns that Haffenreffer’s explanation of “an unpleasant sensation leading to the desire to scratch”, was lacking important information about symptoms, stage and emotional and causal attributes.
Separating out the sensation of itching from its initial cause, the new definition covers three elements: pruritus as a sensation, a description of scratching and the “itch-scratch” cycle, and the definition of “chronic pruritus” as a condition lasting six weeks or longer.
“Pruritus is devastating, and the new definition sets out to facilitate healthcare, communication with decision-making bodies, and, importantly, the first step towards researching and developing suitable treatments,” reported the panel behind the new definition in Journal of the European Academy of Dermatology and Venereology [link here].
The 130 participants, who arrived at the new wording after a Delphi process, agreed that pruritus was a sensation that can be defined as “an unpleasant sensation of the skin and/or neighbouring mucous membranes, commonly triggering an urge to scratch”, and that it can be “can be triggered, worsened or improved by a broad variety of external and internal factors”.
Chronic pruritus, meanwhile, can be both a symptom of other diseases but also an independent disease in its own right.
Defined as either intermittent or continuous over a period of at least six weeks, the Delphi reviewers agreed the chronic condition can vary substantially in course, extent and location, and can “impact on personal, social or professional quality of life and health”.
The review agreed that while chronic pruritus can be a symptom of disease, it can also persist despite the resolution of an original disease and can go on to become an independent condition in its own right.
“[Chronic pruritus] can persist independently of the stage or presence of the underlying aetiology,” the reviews authors explained.
The acknowledgment of the wide differences in duration, location and impact of chronic itching “clearly describes the characteristics of CP, including inter-individual fluctuations and the induction of distress, which is the most significant individual effect”, the authors said.
The last three statements to find consensus relate to scratching, including an acknowledgment that prolonged itching may lead to an itch-scratch cycle. This helps “explain the role of scratching and how it promotes the chronicity of pruritus”, the reviewers said.
Acknowledging both sensation and disease
The authors said the new definition does a better job of reflecting the complexity of the sensation of pruritus, its duration and the way it can affect a patient’s emotions and lifestyle.
The new definition “separates the sensation from the initial cause, considering it an independent disease, as it has already been implemented for pain”, they said.
It was hoped the updated definition would improve communication about the experience of pruritus and improve treatment pathways, they added.