With the exception of pollen protein, all allergenic proteins have high stability to digestive enzymes. Therefore this stability can be used as an indicator of the potential of a protein being an allergen (Astwood, 1996). It has been reported that proteins that are rapidly hydrolyzed to peptides and single amino acids smaller than 3.5 kDa by pepsin can be considered less likely to be allergenic (Fu et al., 2002). And if protein allergens are to reach and pass through the intestine mucosa to elicit an allergenic response, they must be able to resist peptic and tryptic digestion and the acid conditions of the digestive system. The Cry1Ab/Ac protein was degraded rapidly by digestive enzymes as assessed by both SDS–PAGE and Western Blot. These results suggest, but do not prove, that the protein has no allergenic activity, since the correlation between resistance to proteolysis and allergenic activity is not absolute (Fu et al., 2002).