What causes chilblains (pernio)?

Chilblains, or pernio, are caused by exposure to cold temperatures, particularly when the skin warms too quickly after being chilled. This condition occurs when the small blood vessels in the skin become inflamed in response to cold exposure, leading to painful, itchy lesions, typically on the fingers and toes.

When the body is exposed to cold, blood vessels constrict to preserve heat. If the area then warms up too quickly, the vessels can still be inflamed and may not function properly, allowing blood to leak into the surrounding tissues. This results in the characteristic symptoms of chilblains. Understanding this mechanism highlights the importance of gradual warming of cold-exposed areas and proper clothing to prevent the condition.