Is Gelatin or BSA best for blocking in immunofluorescence?

Gelatin does not contain serum proteins that cross-react with mammalian antibodies, potentially making it a better choice than BSA due to less background. However, it can still mask some antigens. Another limitation of gelatin is that it contains endogenous biotin. Because of this endogenous biotin, gelatin cannot be used with biotin detection systems. Thus, the choice to use gelatin or BSA depends on the experiment.