At what percentage does alcohol begin to lose its efficiency when diluted?

The correct percentage at which alcohol begins to lose its efficacy when diluted is 70%. This is largely due to the fact that alcohol needs to maintain a certain concentration to effectively kill bacteria and viruses. At 70% concentration, alcohol can penetrate the cell walls of microorganisms more effectively, leading to cellular damage and eventual death.

When alcohol is diluted to a concentration lower than this, its ability to denature proteins and disrupt cell membranes decreases, which means it is less effective as a disinfectant. In contrast, higher concentrations of alcohol (like 90% or 80%) evaporate more quickly and may not remain in contact with surfaces long enough to achieve effective disinfection.

Thus, using alcohol at 70% ensures optimal disinfectant properties while balancing efficacy and drying time, which is crucial for sanitation purposes in esthetics and general hygiene practices.