Figure 4

Verification of the effect of lactic acid on hand antimicrobial activity. (A) Amount of lactic acid on the surface of the hands of the participants (N = 54). (B) Bactericidal effect of applying lactic acid onto the hands of the participants. The test was made in a 2 cm × 2 cm area on the palm. After hand washing, 10 µL of 0.2, 1.0, 5.0, 10, and 23.5 g/L lactic acid aqueous solutions along with pure water as control were applied on the test site, followed by drying for 5 min. Then, 10 µl of the bacterial solution (E. coli, OD = 1.0) was added to the test site, spread for 30 s, and dried for 3 min. The amount of applied lactic acid on skin surface is plotted along X axis. The log reduction value denoting the relative logarithmic reduction of viable bacteria at each lactic acid amount and control is plotted along Y axis.