In response to COVID-19, the surge in hand sanitizer production has left alcohol in short supply. In relation, repeated hand sanitizing and cleansing can damage the skin barrier, which has driven the search for gentler, alcohol-free alternatives.
Taken together, formulators have turned to benzalkonkium chloride as a solution to the supply shortage that also offers alcohol-free efficacy. Here, we highlight two studies showing this antibacterial and antiviral efficacy, in support of its potential utility in hand sanitizers.
First, a study published in 2019 in the American Journal of Infection Control assessed the efficacy of benzalkonium chloride (BC) as an antibacterial agent. Here, a non-alcohol-based formulation using BC at 0.12% was compared with an ethanol-based formulation at 63% for its bactericidal action against Staphylococcus aureus.
The BC-based product markedly reduced colony-forming units at each of the three time points tested (3.75- to 4.16-log10 reductions). The ethanol-based product produced less than a 1-log10 reduction over the same times. These differences were highly significant.
Several years prior, in 2007, work published in the Japanese Journal of Infectious Disease established the virucidal activity of benzalkonium chloride—which, of course, is especially relevant today. Here, the authors found that benzalkonium chloride was more effective against three specified viruses under given conditions, described next, than sodium hypochlorite (SHC), sodium hydroxide (SH) and ethanol.
The researchers were specifically interested in identifying the most effective virucidal agent to sterilize instrumentation used in the production of vaccines to treat the influenza virus (FluV), Newcastle disease virus (NDV) and avian infectious bronchitis (IBV); all of which, like coronaviruses, are enveloped viruses.
Notably, these vaccines are propogated in the allantoinic fluid present in chicken eggs. As such, the researchers studied the effects of the virucidal agents against these viruses and in the presence of this concentrated protein fluid. Additional details are disclosed in the full article.
Virucidal Efficacy Explained
As stated, the benzalkonium chloride demonstrated strong virucidal activity, which was not dose-dependent. The authors explained this is because it is a cationic soap. The tested viruses, as mentioned, are enveloped, so it was speculated that benzalkonium chloride resolved the virus envelope as a detergent, and that activity may select negatively charged viruses due to electrostatic interactions. On the other hand, the SHC, SH and ethnol are said to rely on Brownian motion.
In the end, the researchers concluded benzalkonium chloride is a useful virucidal agent, especially for FluV, NDV and IBV viruses. Furthermore, it is safe for human use and the U.S. Food and Drug Administration has approved its use for hand sanitizer applications.