Psoriasis: the hidden mechanism behind the itching

© Script: Jeanne Fenouil and Sacha Tembe - Filmmaking: Jeanne Fenouil (video in french, english subtitles available translated by AI)

Did you know that we’ve finally figured out why psoriasis is so itchy?

125 million people worldwide live with this condition, unable to stop themselves from scratching. In 2025, the WHO even classified skin diseases as a global health priority. And among them is psoriasis.

We’re familiar with its characteristic red patches, but it’s often the chronic itching (pruritus) that’s the most debilitating… and the hardest to treat.

Nicolas Bouladoux explains the mechanism that our teams at the Pasteur Institute have just uncovered.
During an inflammatory response, the immune system overreacts against bacteria naturally present on the skin. This reaction releases a molecule, the cytokine IL-17A, which acts directly on sensory neurons and triggers abnormal proliferation of nerve endings. The result: the skin becomes hypersensitive, and the itching intensifies in a vicious cycle.

By precisely targeting this mechanism, we may finally be able to develop effective treatments for chronic pruritus, a symptom that is still inadequately managed today. This breakthrough opens up new therapeutic avenues for millions of patients.