We propose a simple and accessible model of lactobacilli adhesion to human erythrocytes. The influence of bivalent cations on the surface charge of erythrocytes and lactobacilli Streptococcus thermophilus and their adhesive interaction has been investigated. We have shown that, despite the seemingly similar unidirectional effect of Ca2+ and Mg2+ cations, the cause of decreased adhesion lactobacilli S. thermophilus to human erythrocytes differ. While Ca2+ ions affect the surface charge of erythrocytes, not changing it in S. thermophilus, Mg2+ ions, conversely, affect the surface charge of lactobacilli and do not change it in erythrocytes. Our results confirm our proposition that in this case, the bivalent cations affect the second irreversible stage of adhesion process, but not the physical interactions during the first reversible stage.