Perniö (; ) is a former municipality of Finland. It was consolidated with Salo on January 1, 2009.

Chilblains — also known as pernio and perniosis — is a medical condition that occurs when a predisposed individual is exposed to cold and humidity, causing tissue damage. It is often confused with frostbite and trench foot. Damage to capillary beds in the skin causes redness, itching, inflammation, and sometimes blisters. Chilblains can be reduced by keeping the feet and hands warm in cold weather, and avoiding extreme temperature changes. Chilblains can be idiopathic (spontaneous and unrelated to another disease), but may also be a manifestation of another serious medical condition that needs to be investigated. A history of chilblains is suggestive of a connective tissue disease (such as lupus). Chilblains in infants, together with severe neurologic disease and unexplained fevers, can be seen in Aicardi–Goutières syndrome, a rare inherited condition.