An astonishing research development is the discovery that our immune system actually uses chlorine, bromine and Iodine to halogenate and kill invading microorganisms. For example, cellular enzymes in mammalian white blood cells oxidize natural blood chloride (bromide and iodide) into active chlorine. This causes the death of pathogens (bacteria, yeast, fungi and even tumor cells) by chlorination. chlorination is apparently as natural a biological process as blood clotting or salivation.