Lactic acid and lactates are widely used as natural preservatives. Even at neutral skin pH and higher, the MIC value (Minimal Inhibitory Concentration: the concentration at which microbial growth no longer occurs) is relatively low (see table).

The table shows that the incorporation of lactic acid (or lactates) in cosmetic products improves the stability of the formulation against bacterial growth. It can also clearly be seen that at neutral skin pH values (pH 5-7) the effect of citric acid is practically zero.