Lewisite is a chemical compound that was developed as a chemical warfare agent during World War I. It is classified as a blister agent, meaning it can cause severe skin and eye irritation, as well as damage to the respiratory system. Lewisite has a distinctive odor similar to geraniums, which can help identify its presence. The compound is a member of the arsenic family and is known for its toxic properties. Although it was never used in combat during WWI, lewisite remains a concern due to its potential use in chemical warfare and the challenges associated with its disposal and decontamination.