Millions of US consumers spend nearly $1 billion annually on “antibacterial” and “antimicrobial” soap, but is it really better than plain soap? A recent study shows little significant difference between the bactericidal effects of plain soap and antibacterial soap when used under real-life conditions.
Handwashing with soap and water is an important and inexpensive method for preventing the transmission of disease, as it removes contaminants, including pathogenic bacteria or viruses, from hands.
Antibacterial hand washes have proliferated in the fight against harmful germs. “Antibacterial” refers to soap containing ingredients with active antimicrobial activity, of which triclosan is the most common. Plain soap, on the other hand, contains no such ingredients.
Yet, there is some controversy over the effectiveness and safety of antibacterial products. In December 2013, the US Food and Drug Administration (FDA) proposed a rule stating that manufacturers must provide data to demonstrate that antibacterial soap is more effective than plain soap or water.
A team from the Korea University in Seoul, led by Dr. M.S. Rhee, set out to investigate whether this is the case, putting focus on triclosan.
Triclosan is a phenoxyphenol antimicrobial agent first developed in the early 1960s and widely used as an antibacterial or antifungal agent since the 1970s.
It is added to various personal care products and cosmetics, including soap, toothpaste, lotions, shampoos, even clothing, kitchenware, furniture and toys, with the aim of reducing or preventing bacterial contamination and growth.
- An estimated 50% of diarrheal-associated deaths could be prevented by handwashing
- Researchers estimate that if everyone routinely washed their hands, a million deaths a year could be prevented
- Handwashing can reduce the risk of respiratory infections by 16%.
Triclosan has proven effective against bacteria, fungi and viruses. However, adverse effects have been reported, including allergies, antibiotic resistance, endocrine disruption, acute/chronic toxicity and bioaccumulation; one study even identified carcinogenic impurities.
The evidence of antibacterial soap’s effectiveness compared with plain soap is, moreover, inconclusive.
The researchers compared the two types of soap through in vitro and in vivo experiments. Their findings have been published in the Journal of Antimicrobial Chemotherapy.
The soaps were exposed to 20 bacterial strains, recommended by the FDA, and tested under conditions that replicated handwashing recommendations and consumer habits.
Both products contained the same ingredients, except for the addition of 0.3% triclosan (the maximum amount allowed by law) to the antibacterial version. Exposure to microbes was for 20 seconds, the time suggested for effective handwashing by bodies such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). Temperatures used were 22 ºC and 40 ºC, to represent the “warm” temperature recommended for use with soaps.
While “warm” water is recommended for handwashing, how warm is not usually specified by manufacturers, although the American Society for Testing and Materials (ASTM) suggest 40 ºC for testing. Thus, soaps have hitherto been tested at 40 ºC, although most consumers wash their hands with “whatever water comes from the tap.”
The in vitro test was performed at 22 ºC and 40 ºC, and the 16 in vivo participants washed their hands in tepid water of 40 ºC.
The volunteers followed handwashing guidelines specified by the WHO, including lathering the soap vigorously for 30 seconds, and spreading it over the entire surface of the hands and the lower third of the forearms.
The results showed no significant difference in bactericidal activity between plain and antibacterial soap at either 22 ºC or 40 ºC degrees during the 20 seconds allowed for the experiment. After 30 seconds, there was still no difference. It seems that under “real life” conditions, antibacterial soap containing triclosan (0.3%) is no more effective than plain soap at reducing bacterial contamination.
After 9 hours, antibacterial soap showed significantly greater bactericidal effects, suggesting that although soap containing triclosan does have antibacterial effects, these do not occur during the short time required for handwashing.
Triclosan is known to have antibacterial and antifungal properties, so why was no difference observed in this experiment? The researchers propose two main reasons.
First, exposure time was too short. Most previous studies have followed standards requiring continuous exposure to soap for at least 24 hours. When Escherichia coli ATCC 25922 was exposed to antibacterial soap containing 0.3% triclosan, the cells survived for up to 24 hours, compared with 72 hours after exposure to plain soap. After 6 hours, there was little difference between the two. It would seem that 20 seconds’ exposure is not long enough to make a difference.
Second, the soap used in this study contained detergents and surfactants such as sodium laureth sulphate, which may reduce the bactericidal effects of triclosan.
Previous studies have shown tricolosan to be effective in soaps, but only at levels of 0.3% or higher; 0.3% is the maximum amount of triclosan allowed in soaps. They also compared commercial soaps, so the formulation of the plain and antibacterial soaps may not have been identical, possibly affecting the results.
The Korean scientists therefore suggest that their data may be a more accurate reflection of the effectiveness of these soaps.
They also suggest it may be time for governments and industries to review rules governing the labelling of “antibacterial” soaps. A survey on soap manufacturers between July and August 2014 revealed that many had already removed triclosan from their products as a result of the FDA’s proposed rule in 2013.
The Korean researchers suggest addressing advertisements and consumer belief regarding the effectiveness of antibacterial soaps, with possible implications for international consumer laws.Medical News Todayscrutiny of antibacterial soaps