['Type I hypersensitivity reactions caused by latex products are ascribed to proteins eluted from them, but little is known about the properties of these allergenic proteins. The reason for the cross-reaction between rubber latex and fruits is also not known. We have speculated that a series of defense-related proteins in plants is a cause of latex allergy and the cross reaction.', 'To verify our hypothesis, we selected a lysozyme as a representative defense-related protein and examined its relationship to latex allergy.', 'Lysozymes eluted from latex gloves were detected with a cell-suspension clearing test. A chromatographically separated lysozyme was investigated for its physicochemical and enzymatic properties and allergenicity.', 'Lysozyme activity was detected in extracts from ammoniated latex and latex gloves. We separated a lysozyme (27 kd; isoelectric point, 9.5) using cation-exchange and gel filtration chromatography. This lysozyme was enzymatically very similar to fruit lysozymes and was demonstrated to be an allergen.'] Is one of the rubber latex allergens a lysozyme?