Freshly tapped latex was fractionated by ultracentrifugation into rubber layer, C-serum and bottom fractions. The bottom fraction was used for B-serum, bottom membrane protein (BMP) and BM proteolipid (BMPL) preparations. SDS-PAGE immunoblotting revealed the presence of IgE-binding proteins in the C-serum, B-serum, BMP and BMPL fractions but not the rubber layer. The binding of IgE to 33 kD BMPL was observed in all tested sera with positive skin prick test and latex allergy history. An ELISA test was performed to evaluate IgE-binding capacity of the proteins present in C-serum, B-serum and BMP, by using many serum from local latex glove factory workers. The most reactive IgE-binding fraction was identified to be BMP. Similarly, the IgE in serum with high BMP-binding capacity was shown to bind a 33 kD proteolipid isolated from kiwi fruits. Cross-reactivity between 33 kD latex and kiwi proteolipids was revealed from SDS-PAGE immunoblotting inhibition experiment. Moreover, proteins of similar molecular weight around 30 - 33 kD, known as predominantly cross-reactive allergens among banana, latex and avocado, were also isolated as proteolipids in banana, avocado and chestnut. These findings suggest a common presence of (cross-reactive) proteolipid allergens. Hence, a hydrophobic means to eliminate these lipid-soluble allergens seems to be an important solution in preventing latex allergy as well as latex-fruit syndrome.