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CRYOGENS
CRYOGENS
Presently, liquid nitrogen is used exclusively in the vast majority of dermatology settings. However, prior to its development, several other cryogenic substances were employed for similar purposes. The original cryogen was liquefied air (โ190ยฐC), which was composed of approximately 78% nitrogen, 21% oxygen, 1% argon, with traces of other gases.2,3 While effective, liquid air was difficult to obtain, and was subsequently superseded by solidified carbon dioxide (โ78.5ยฐC) in the early 1900s.4 In the 1920s, liquid oxygen (โ182.9ยฐC) became readily available, but its use was limited by safety concerns including flammability.5 The use of liquid nitrogen (โ195.6ยฐC), which remains the most frequently employed cryogen, was first reported in 1950.3 In contrast to liquid oxygen, liquid nitrogen is inert, and is considered to be both safe and effective.