Monocytes, macrophages, neutrophils, and eosinophils are able to generate and release reactive oxygen species. The reactive oxygen species are generated by reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase which is activated by a number of different soluble and particulate agents. This activation results in the reduction of molecular oxygen to the potentially toxic oxygen species superoxide anion (O₂ ⁻ ), or hydrogen peroxide (H₂ O₂ ), with NADPH serving as the electron donor. In the presence of eosinophil peroxidase, H₂ O₂ may then give rise to the potentially cytotoxic hypohalous acids such as HOBr. The increase in oxygen consumption is termed the respiratory burst (1 ,2 ).