Can You Catch an Infection From Sharing a Bar of Soap?

sharing bar soap

Story at-a-glance -

  • Hand-washing is a critical function to remove germs and avoid getting sick, but many believe bar soap harbors these same disease-causing germs, increasing their risk of illness
  • Rigorous studies have proven bar soap may sometimes be messy, but it does not transfer germs to your skin, even after being inoculated by millions of bacteria, while antibacterial products require at least two minutes of contact with your skin to work
  • The FDA banned the use of triclosan in antibacterial soaps but continues to allow triclosan in hospital products, hand sanitizers and toothpaste, despite studies demonstrating damage to your health and the environment
  • Using proper hand-washing technique with bar soap is an effective means of protecting your health and the environment

By Dr. Mercola

Germs are everywhere. According to Charles Gerba, microbiologist at the University of Arizona,1 your kitchen is the heart of your home, and the heart of its germs. Some of the places in your kitchen that may be dirtier than a toilet include your kitchen sponge, sink, cutting board, refrigerator door handle and kitchen countertops.

According to Dr. Neil Schachter, author of “The Good Doctor's Guide to Colds and Flu,”2 some of the germiest community places include public restrooms, your child's school or day care, public transportation and your doctor's office. In response to heavy advertising campaigns warning of germ-laden objects, many have turned to using antibacterial soap.

In fact, one survey found 74 percent of Americans use antibacterial soap and 75 percent of mothers with children said removing antibacterial soap from the market would make them angry.3 However, it is important to note antibacterial soaps are only effective if left on the skin for a minimum of two minutes.4 As sales of liquid antibacterial soaps in pump bottles rise, bar soap sales are falling.

According to research by a marketing intelligence agency, bar soap sales fell 5 percent between 2010 and 2015 as the soap suffers from negative perceptions. Nearly 48 percent of consumers believe bar soap may be a haven for bacteria, and younger consumers believe this more than others.5

You Won’t Get Sick From Bar Soap

The Centers for Disease Control and Prevention (CDC)6 calls hand-washing “a do-it-yourself vaccine” as it is one of the best ways to remove germs, avoid getting sick and prevent the spread of illness. However, while removing germs may limit the spread of infection, the addition of antibacterial chemicals may increase your risk of other negative health conditions. Although millennials believe bar soap may harbor bacteria, research proves this isn't true.

The first rigorous study to answer this question was published in 1965.7 Researchers intentionally contaminated their hands with nearly 5 billion bacteria, including disease-causing strains such as staphylococcus and E. coli. They then washed their hands with bar soap, after which a second person washed with the same bar of soap. The second person's hands were cultured and researchers found the bacteria were not transferred. They concluded:8

  • Bar soaps do not support the growth of bacteria under usage conditions.
  • Bar soaps are inherently antibacterial by their physical-chemical nature.
  • The level of bacteria that may occur on bar soap, even under extreme usage conditions (heavy usage or poorly designed nondrainable soap dishes), does not constitute a health hazard.

Nearly 20 years later, another study9 (sponsored by a soap manufacturer) confirmed these findings. Here, they inoculated bars of soap with pathogenic bacteria; 16 participants washed their hands with those bars. After washing, none of the participants’ hands had detectable levels of bacteria. According to the researchers,10 “little hazard exists in routine hand-washing with previously used soap bars and support the frequent use of soap and water for handwashing to prevent the spread of disease.”

The CDC continues to recommend hand-washing as a primary defense and endorses bar soap and liquid soap.11 Occasional studies have documented environmental bacteria on bar soap, but no study has demonstrated bar soap to be a source of infection.12

What’s more, by using bar soap you avoid contributing to the estimated 270 million plastic pump bottles added to the trash annually. Since most people use seven times more liquid soap per wash than bar soap, you also reduce your family’s expenses, as bar soap is less expensive.13

Ditch Your Antibacterial Liquid Soap

Have you ever thought about how many times a day you wash your hands with soap? While it has an impressive track record to maintain your health, with each hand washing your body may absorb just a little bit of what you're washing your hands with. Manufacturers have tried to convince consumers that using antibacterial compounds is the best way to reduce your exposure to disease-causing germs.

But according to the FDA, there isn't enough science to demonstrate over-the-counter antibacterial soaps are better at preventing illness then washing with plain soap and water.14 After evaluating the available literature, the FDA issued a proposed rule requiring manufacturers to provide information about the safety and efficacy of antibacterial compounds if they wanted to continue marketing those products.15

Very little information was provided by the manufacturers, leading the agency to issue a final rule that consumer antiseptic washing products containing 19 bacterial additives, including triclosan and triclocarban, could no longer be marketed. Dr. Theresa Michele from the FDA’s Division of Nonprescription Drug Products said:16

“Following simple hand-washing practices is one of the most effective ways to prevent the spread of many types of infection and illness at home, at school and elsewhere. We can't advise this enough. It's simple, and it works.”

While the rule17 affects products intended for use with water, it does not affect hand sanitizers, wipes, toothpaste18 and antibacterial products used in the health care setting.19 In response to comments submitted by manufacturers, the FDA deferred making a rule on three additional ingredients, including benzalkonium chloride, benzethonium chloride and chloroxylenol (PCMX). The rule is part of a broader effort to reduce the overall consumer use of antibacterial products and potentially reduce bacterial resistance.20

However, while the FDA collects information on these three additional antibacterial compounds in consideration for use in antibacterial soaps, research already exists demonstrating effects on human health and the environment.

Benzalkonium chloride. This compound is commonly used in cosmetics as an antimicrobial agent.21 Today it is restricted for use in cosmetics in Canada and Japan.22 The compound has repeatedly demonstrated toxicity in experimental, laboratory and clinical studies, as well as environmental pollution.23

In a study evaluating the safety of the compound, researchers found it was commonly used in concentrations up to 5 percent, but data analysis concluded the compound could be safely used at concentrations up to just 0.1 percent.24

It may cause extensive damage to the eyes and deeper ocular tissues, appears to be very toxic to aquatic life, and when burned, it produces toxic fumes including chlorine, nitrogen oxide and ammonia.25 Prolonged exposure may produce side effects such as rashes, allergic reactions, redness, swelling and blisters. Long-term exposure may lead to asthma, chronic dermatitis and other immune-mediated disorders.26

Benzethonium chloride. Also restricted in cosmetic use in Canada and Japan,27 the toxic effects include skin and tissue irritation. This may be especially uncomfortable as it is a spermicide triggering vaginal irritation with burning and itching.28 When in contact, users may experience eye irritation and corneal damage.

Genotoxic effects have been demonstrated in the laboratory in concentrations commonly found in wastewater.29 While this may have a significant impact on the environment, it is important to note wastewater treatment plants are not setup to remove these types of synthetic ammonium salts30 from effluent.31

PCMX. This is a persistent chemical that bioaccumulates in the environment and has been linked to organ system toxicity.32 It is classified as a skin irritant and toxic or harmful by the European Union. The chemical is known to cause contact dermatitis and potentially trigger skin allergies.33 The chemical is highly toxic to fish34 and found in wastewater effluent.35

Triclosan Poses Dangers to Your Health and the Environment

Although the FDA has effectively removed triclosan from antibacterial products requiring water to rinse your hands, it continues to remain in hand sanitizers, wipes, toothpaste and a number of other products. This ingredient has been linked to allergies, thyroid dysfunction, endocrine disruption, weight gain and inflammatory responses.36 Triclosan has also been found to aggravate the growth of liver and kidney tumors.37

Endocrine disruption is a serious concern as it may lead to a wide variety of health problems including breast, ovarian, prostate and testicular cancers.38 It has also been associated with preterm and low birth weight babies, precocious puberty in girls and undescended testicles in boys.

Exposure to even low levels of triclosan has been found to disrupt thyroid hormone associated gene expression. This in turn may alter the rate of thyroid hormone mediated post embryonic development in amphibians.39 According to Dr. Janet Woodcock, director of the FDA Center for Drug Evaluation and Research:40

“Consumers may think antibacterial washes are more effective at preventing the spread of germs, but we have no scientific evidence that they are any better than plain soap and water. In fact, some data suggests that antibacterial ingredients may do more harm than good over the long term.”

Long term negative effects of triclosan are also related to damage to the environment. The use and disposal, washing down the drain, of products containing triclosan discharges this toxic chemical into the environment and ultimately through wastewater treatment plants. In 2007, the Environmental Working Group41 partnered with researchers and found 40 percent of waste water samples collected from the San Francisco Bay Area contained triclosan.

After leaving wastewater treatment plants, triclosan may also be found in farm fields where wastewater residues may be applied as fertilizer, contaminating produce grown in the fields.42 Triclosan contamination is not removed by typical wastewater treatment methods.43

It's been found in activated sludge, surface water and sediments, and according to one study44 of 95 different organic wastewater contaminants in U.S. streams, triclosan was one of the most frequently detected compounds at some of the highest concentrations.

This prevalence is concerning as triclosan is converted into dioxin when exposed to sunlight in a water environment. It can also combine with chlorine to form chloroform. Both of these chemicals are known human carcinogens. As a result of being lipophilic, absorption and bioaccumulation in fatty tissues of aquatic organisms has been found. The effect on amphibian activity of natural hormones has suggested triclosan maybe an endocrine disruptor in amphibian life.45

How Does Soap Work?

To fully understand the CDC's assertion that soap and water is as effective as antibacterial soap, it's important to understand how soap works. A soap molecule is suited for mixing oil and water as it shares qualities of each. Ancient soap recipes dating back to Roman times46 included rendered fat from a cow or sheep, mixed with an alkaline substance, such as water mixed with ash. This produced a brown curd efficient at getting dirt to wash away.

Soap molecules are amphipathic,47 meaning they have both polar and nonpolar properties, giving them the ability to dissolve most kinds of molecules. The alkaline substance helps create a polar head at one end or an electric charge making it hydrophilic (water-loving).48 Hydrogen atoms in water molecules have a slightly positive charge, so when you wet your hands and then use soap, this molecule will readily bond with the nearest water molecule.

Soap also contains a hydrophobic fatty acid component, so it easily latches onto other hydrophobic compounds, such as grease.49 Together, the hydrophilic and hydrophobic characteristics of soap help to lift away oil, other grime and germs, suspending them in the water. Additional water helps to wash the suspended droplets away.

This is the chemical aspect of how soap works. When using soap, you also tend to wash your hands longer trying to rinse all the soap off your hands.50 Regular soap doesn't necessarily kill the bacteria and viruses as much as it helps you to wash them off your skin.

Removal of bacteria and viruses from your skin is a critical means of maintaining your health and wellness. You don't need the antibacterial properties of chemical compounds in order to maintain your health, but these antibacterial compounds may cause health problems and contribute to damaging the environment.

A home demonstration of the chemical properties of soap at work51 starts by adding a little grease and water to a jar. Cap it tightly and shake. After a couple of minutes the oil and water begin to separate, in much the same way oil and vinegar separates. Now, add a little dish soap to the mixture and shake again. After several minutes, the mixture will be cloudy but will not have separated as the oil and water have mixed through a chemical reaction with the soap.

Proper Hand-Washing Technique Your Best Defense Against Germs

Correctly washing your hands may potentially reduce bacteria transferred from person to person. In a study using military recruits, researchers found teaching simple hand-washing in a large Navy training center resulted in a 45 percent reduction an outpatient visits for respiratory illnesses.52 To be truly effective for disease control, make note of the following guidelines:

  • Use warm, running water and a mild soap.53
  • Start with wet hands, add soap and work up a good lather, all the way up to your wrists, scrubbing for at least 15 or 20 seconds. A good way to time this is to sing the "Happy Birthday" song twice.
  • Make sure you cover all surfaces, including the backs of your hands, wrists, between your fingers and around and below your fingernails.
  • Rinse thoroughly under running water.
  • Thoroughly dry your hands, ideally using a paper towel. In public places, also use a paper towel to open the door as a protection from germs living on the handles.
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