The switch from bar soap to liquid has been driven by a fear of bacteria lurking on bar soap. Companies encouraged the notion that using liquid soap was more hygienic.

This NY Times article which asked “does each member of the family need an individual bar of soap to prevent spreading germs, or do we have to switch to liquid soap?” came to a very different conclusion. It cites studies that concluded washing even with contaminated bar soap is unlikely to transfer bacteria, especially if the bar gets rinsed off between uses. According to the NY Times:

“… soap bars were inoculated with E. coli and P. aeruginosa bacteria at levels 70 times as high as those reported on used soap bars. Then, 16 people were told to wash their hands as usual with the inoculated bars.

“After washing, none of the 16 panelists had detectable levels of either test bacterium on their hands,” the researchers wrote. “These findings, along with other published reports, show that little hazard exists in routine handwashing with previously used soap bars and support the frequent use of soap and water for handwashing.”

So how can a bar of soap have bacteria on it and yet not spread germs? Simply, washing is a two step process. When you lather up the oil attracting end of the soap molecule picks up grease and oils on your skin. When you rinse, the water attracting end of the molecules follow the water, letting you rinse the soap molecules — and their attached impurities — away.

This leads us to the next question “if liquid soaps provide no hygiene benefit, why have companies been so aggressive in marketing liquid body washes?” This article on US website DailyFinance may provide a clue. Their comparison showed bathing with the recommended amount (2 teaspoons) of Olay body wash cost HK$1.33 per wash while bathing with Ivory bar soap cost just over HK$0.09, providing a significant profit motive for companies to get us to switch.

Another often cited advantage of liquid body wash is that it allows manufacturers to add moisturizers. While a complaint against bar soap is that it may be harsh and drying. In fact, there are many varieties of bar soaps in the market that contain glycerine and natural oils that moisturize the skin. These soap can be just as gentle and mild on the skin, negating any advantage of body washes. If body washes have no advantages, do they have any disadvantages? It turns out there are many.

Containing lots of water, body washes are also much heavier than bar soap, resulting in a significantly higher carbon footprint for transportation. Packaging for body washes are made of plastic that ends up in the landfill or our oceans (see picture below). Bar soap has a clear edge in transportation, packaging and disposal.

Lastly, lets take a look at what’s inside. Most liquid body washes are made of petroleum, while many traditional bar soaps are made of saponified animal fat and plant oils. Liquid soaps need the addition of emulsifying agents and stabilizers to maintain their consistency. Although these chemicals may have been approved by the relevant authorities for use on humans, the testing procedures do not include the consequence of long term use or interactions between these and the myriad of other chemicals in our environment. For example, diethanolamine (DEA) is commonly added to confer a creamy texture and foaming action. It inhibits in baby mice the absorption of choline (not to be confused with chlorine), which is an essential nutrient necessary for brain development and maintenance. High concentrations of DEA were also found to induce body and organ weight changes, and mild blood, liver, kidney and testicular systemic toxicity in mice. A 2009 study also found that DEA is potentially toxic for aquatic species.

I can only conclude then that liquid body washes really provide little or no benefits to the consumer, create significant profits for manufacturers, and are tremendously harmful to the environment. So are you ready to switch back?