Alpha-Gal is a glycoconjugate present on cell membranes of non-primate mammals and bacteria, but not in humans, who display anti-Gal antibodies (ABs) in high titres. Probiotics contain bacterial strains which colonize the intestinal tract. In the present study, we investigated whether intake of fermented milk containing Lactobacillus casei (FML) affects anti-Gal AB titres. Serum was drawn from healthy probands (n = 19) for 6 weeks. After the second week, the probands consumed 125 ml of FML per day. Anti-Gal ABs of all isotypes and cytokines were measured. Bacterial cultures were bred from FML and bacteria were stained for alpha-Gal. Concentration of bacteria in FML was manifold higher than in conventional yoghurt (2 × 10(5)/g yoghurt vs. 1.1 × 10(7)/g FML). Both stained highly positive for Alpha-Gal. Alpha-Gal-specific ABs and cytokines remained unaffected by FML intake. Our results indicated that the consumption of FML does not elicit a humoral immune response in healthy adults.