The evolving vesicular patch test reaction served as a huma model for immunologically induced epidermal damage. We observed that inhibitory factor(s) were detectable in the homogenates only after epidermal disruption had appeared. Maximum inhibition correlated with acute changes seen histologically in the evolving patch test reaction. During resolution of the patch test reaction, the presence of inhibitory factor(s) in the skin homogenates became undetectable. A white ring similar to the Woronoff ring described after ultraviolet light and coal tar therapy of psoriatic plaques was reproduced surrounding the vesicular patch test reaction, suggesting that the inhibitory substance(s) detected following epidermal trauma of various types (physical, immunologic, inflammatory, etc.) functioned in vivo in a similar fashion. Our results suggests that Woronoff's ring is a nonspecific phenomenon that can be formed following various types of trauma to the skin rather than a specific occurrence associated only with the treatment of psoriatic plaques.
