The invention generally relates to compositions of hypochlorous acid (HOCl) and methods of manufacture thereof. In certain aspects, the invention provides air-free compositions of HOCl. In other aspects, the invention provides methods of making HOCl that involve mixing together in water in an air-free environment, a compound that generates a proton (H+) in water and a compound that generates a hypochlorite anion (OCl−) in water to thereby produce air-free hypochlorous acid.