The humble bar of soap is on the decline. According to marketing intelligence agency Mintel, households that stock the blocky chunks of lye are down 5 percent from 2010. Roughly half of polled consumers—particularly those in younger demographics—think the bars might harbor greater amounts of bacteria than their liquid-dispensed counterparts.
Are they correct—or is bar soap getting a bad rap?
The answer might be a little bit of both. Bar soap does indeed tend to let bacteria idle on its surface, but that’s not necessarily going to be a problem. In 1988, the Dial corporation subsidized a study [PDF] in which they purposely drowned bar soap in illness-generating ick like E. coli at levels 70 times higher than what would be found with typical household use. After washing with the infected bars, a test group of 16 hand-washers had no detectable levels of the germs on their hands.
While the research needs an asterisk due to the sample size and its corporate sponsor, it’s also true that there’s never been any reported outbreak of infection as a result of bar cleansers. Washing the surface of your skin is always intended to reduce—not totally eliminate—the number of contaminants to give your immune system a better chance of resisting infection and disease. You'll never be able to totally absolve yourself—or the soap—from grime.
Both bars and liquids are required by the FDA to have antimicrobial ingredients to help minimize the cultivation of bacteria. (This is true even if the soap is not labeled "antibacterial.") And while liquid cleansers might appear to be sealed off against gunk, they’re not necessarily immune to problems during manufacturing: A number of liquid soaps have been recalled in recent years due to staph and Pseudomonas contaminations.
Liquid or solid, soap should be good for about a year before it loses the ability to keep bacteria from proliferating. But if you’re taking that long to go through a small supply, deliberating over the relative effectiveness of a bar should be the least of your concerns.