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At the molecular level, soap breaks things apart. At the level of society, it helps hold everything together.
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By Ferris Jabr
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It probably began with an accident thousands of years ago. According to one legend, rain washed the fat and ash from frequent animal sacrifices into a nearby river, where they formed a lather with a remarkable ability to clean skin and clothes. Perhaps the inspiration had a vegetal origin in the frothy solutions produced by boiling or mashing certain plants. However it happened, the ancient discovery of soap altered human history. Although our ancestors could not have foreseen it, soap would ultimately become one of our most effective defenses against invisible pathogens.
People typically think of soap as gentle and soothing, but from the perspective of microorganisms, it is often extremely destructive. A drop of ordinary soap diluted in water is sufficient to rupture and kill many types of bacteria and viruses, including the new coronavirus that is currently circling the globe. The secret to soap’s impressive might is its hybrid structure.
Soap is made of pin-shaped molecules, each of which has a hydrophilic head — it readily bonds with water — and a hydrophobic tail, which shuns water and prefers to link up with oils and fats. These molecules, when suspended in water, alternately float about as solitary units, interact with other molecules in the solution and assemble themselves into little bubbles called micelles, with heads pointing outward and tails tucked inside.
Some bacteria and viruses have lipid membranes that resemble double-layered micelles with two bands of hydrophobic tails sandwiched between two rings of hydrophilic heads. These membranes are studded with important proteins that allow viruses to infect cells and perform vital tasks that keep bacteria alive. Pathogens wrapped in lipid membranes include coronaviruses, H.I.V., the viruses that cause hepatitis B and C, herpes, Ebola, Zika, dengue, and numerous bacteria that attack the intestines and respiratory tract.
When you wash your hands with soap and water, you surround any microorganisms on your skin with soap molecules. The hydrophobic tails of the free-floating soap molecules attempt to evade water; in the process, they wedge themselves into the lipid envelopes of certain microbes and viruses, prying them apart.
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“They act like crowbars and destabilize the whole system,” said Prof. Pall Thordarson, acting head of chemistry at the University of New South Wales. Essential proteins spill from the ruptured membranes into the surrounding water, killing the bacteria and rendering the viruses useless.
How Soap Works
Washing with soap and water is an effective way to destroy and dislodge many microbes, including the new coronavirus. For more about the virus, see How Coronavirus Hijacks Your Cells.
THE CORONAVIRUS has a membrane of oily lipid molecules, which is studded with proteins that help the virus infect cells.
SOAP MOLECULES have a hybrid structure, with a head that bonds to water and a tail that avoids it.
Spike protein
(helps the virus enter cells)
Hydrophilic head
(bonds with water)
Hydrophobic tail
(avoids water, bonds with oil and fat)
Genetic
material
Lipid membrane
and other proteins
SOAP DESTROYS THE VIRUS when the water-shunning tails of the soap molecules wedge themselves into the lipid membrane and pry it apart.
SOAP TRAPS DIRT and fragments of the destroyed virus in tiny bubbles called micelles, which wash away in water.
Micelle
THE CORONAVIRUS has a membrane of oily lipid molecules, which is studded with proteins that help the virus infect cells.
SOAP MOLECULES have a hybrid structure, with a head that bonds to water and a tail that avoids it.
Spike
protein
Hydrophilic head
(bonds with water)
Hydrophobic tail
(avoids water, bonds with oil and fat)
Genetic
material
Lipid membrane
and other proteins
SOAP DESTROYS THE VIRUS when the water-shunning tails of the soap molecules wedge themselves into the lipid membrane and pry it apart.
SOAP TRAPS DIRT and fragments of the destroyed virus in tiny bubbles called micelles, which wash away in water.
Micelle
THE CORONAVIRUS has a membrane of oily lipid molecules, which is studded with proteins that help the virus infect cells.
SOAP MOLECULES have a hybrid structure, with a head that bonds to water and a tail that avoids it.
Spike protein
Hydrophilic head
(bonds with water)
Hydrophobic tail
(avoids water, bonds
with oil and fat)
Genetic
material
Lipid membrane
and other proteins
SOAP DESTROYS THE VIRUS when the water-shunning tails of the soap molecules wedge themselves into the lipid membrane and pry it apart.
SOAP TRAPS DIRT and fragments of the destroyed virus in tiny bubbles called micelles, which wash away in water.
Micelle
THE CORONAVIRUS has a membrane of oily lipid molecules, which is studded with proteins that help the virus infect cells.
Spike
protein
Genetic
material
Lipid membrane
and other proteins
SOAP MOLECULES have a hybrid structure, with a head that bonds to water and a tail that avoids it.
Hydrophilic head
(bonds with water)
Hydrophobic tail
(avoids water, bonds
with oil and fat)
SOAP DESTROYS THE VIRUS when the water-shunning tails of the soap molecules wedge themselves into the lipid membrane and pry it apart.
SOAP TRAPS DIRT and fragments of the destroyed virus in tiny bubbles called micelles, which wash away in water.
Micelle
THE CORONAVIRUS has a membrane of oily lipid molecules, which is studded with proteins that help the virus infect cells.
Spike
protein
Genetic
material
Lipid membrane
and other proteins
SOAP MOLECULES have a hybrid structure, with a head that bonds to water and a tail that avoids it.
Hydrophilic head
(bonds with water)
Hydrophobic tail
(avoids water, bonds
with oil and fat)
SOAP DESTROYS THE VIRUS when the water-shunning tails of the soap molecules wedge themselves into the lipid membrane and pry it apart.
SOAP TRAPS DIRT and fragments of the destroyed virus in tiny bubbles called micelles, which wash away in water.
Micelle
In tandem, some soap molecules disrupt the chemical bonds that allow bacteria, viruses and grime to stick to surfaces, lifting them off the skin. Micelles can also form around particles of dirt and fragments of viruses and bacteria, suspending them in floating cages. When you rinse your hands, all the microorganisms that have been damaged, trapped and killed by soap molecules are washed away.
On the whole, hand sanitizers are not as reliable as soap. Sanitizers with at least 60 percent ethanol do act similarly, defeating bacteria and viruses by destabilizing their lipid membranes. But they cannot easily remove microorganisms from the skin. There are also viruses that do not depend on lipid membranes to infect cells, as well as bacteria that protect their delicate membranes with sturdy shields of protein and sugar. Examples include bacteria that can cause meningitis, pneumonia, diarrhea and skin infections, as well as the hepatitis A virus, poliovirus, rhinoviruses and adenoviruses (frequent causes of the common cold).
These more resilient microbes are generally less susceptible to the chemical onslaught of ethanol and soap. But vigorous scrubbing with soap and water can still expunge these microbes from the skin, which is partly why hand-washing is more effective than sanitizer. Alcohol-based sanitizer is a good backup when soap and water are not accessible.
In an age of robotic surgery and gene therapy, it is all the more wondrous that a bit of soap in water, an ancient and fundamentally unaltered recipe, remains one of our most valuable medical interventions. Throughout the course of a day, we pick up all sorts of viruses and microorganisms from the objects and people in the environment. When we absentmindedly touch our eyes, nose and mouth — a habit, one study suggests, that recurs as often as every two and a half minutes — we offer potentially dangerous microbes a portal to our internal organs.
As a foundation of everyday hygiene, hand-washing was broadly adopted relatively recently. In the 1840s Dr. Ignaz Semmelweis, a Hungarian physician, discovered that if doctors washed their hands, far fewer women died after childbirth. At the time, microbes were not widely recognized as vectors of disease, and many doctors ridiculed the notion that a lack of personal cleanliness could be responsible for their patients’ deaths. Ostracized by his colleagues, Dr. Semmelweis was eventually committed to an asylum, where he was severely beaten by guards and died from infected wounds.
Florence Nightingale, the English nurse and statistician, also promoted hand-washing in the mid-1800s, but it was not until the 1980s that the Centers for Disease Control and Prevention issued the world’s first nationally endorsed hand hygiene guidelines.
Washing with soap and water is one of the key public health practices that can significantly slow the rate of a pandemic and limit the number of infections, preventing a disastrous overburdening of hospitals and clinics. But the technique works only if everyone washes their hands frequently and thoroughly: Work up a good lather, scrub your palms and the back of your hands, interlace your fingers, rub your fingertips against your palms, and twist a soapy fist around your thumbs.
Or as the Canadian health officer Bonnie Henry said recently, “Wash your hands like you’ve been chopping jalapeños and you need to change your contacts.” Even people who are relatively young and healthy should regularly wash their hands, especially during a pandemic, because they can spread the disease to those who are more vulnerable.
Soap is more than a personal protectant; when used properly, it becomes part of a communal safety net. At the molecular level, soap works by breaking things apart, but at the level of society, it helps hold everything together. Remember this the next time you have the impulse to bypass the sink: Other people’s lives are in your hands.
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FAQs
Why does soap work so well? ›
Here's why it's soap is so effective:
The phospholipids consist of a greasy lipid part that is hydrophobic, meaning it hates water, and a phosphate head group that is hydrophilic, meaning it loves water. The spikes on a coronavirus are made of protein.
There is no evidence that antibacterial soaps are more effective than plain soap for preventing infection under most circumstances in the home or in public places. Therefore, plain soap is recommended in public, non-health care settings and in the home (unless otherwise instructed by your doctor).
How do you test the effectiveness of soap? ›To see how effective each soap was, divide the number of colonies in the test dish by number of colonies in the control dish, then subtract the result from 1 and write the answer as a percentage. You will see multiple round dots of growth; these are bacteria colonies.
What was the purpose of the soap? ›In hand washing, as a surfactant, when lathered with a little water, soap kills microorganisms by disorganizing their membrane lipid bilayer and denaturing their proteins. It also emulsifies oils, enabling them to be carried away by running water.
What are the pros and cons of soap? ›Pros- Bar soaps are often more effective at removing dirt, oil and odors because of the components they are made of. Containing sodium lauryl sulfate and other antibacterial products, bar soaps are often the best way to get your skin clean. Cons- The antibacterial products in bar soap often cause skin to dry out.
What makes a soap good quality? ›A high quality soap made with care and attention will result in a soap that does not cause irritation, even to those with dermatological issues or extreme sensitivities. This requires quality oils, a formula that is as simple as possible, and high quality, skin-safe essential oils or fragrance oils.
What's the number one soap in America? ›Dove. Dove is a personal care brand owned by Unilever, it is also the most popular brand name in the soap markets across over 80 countries in the world. In the USA and the UK – two of the world's largest soap markets – Dove is also the number one soap brand that are dominating the markets.
Why does bar soap work better? ›Bar soap works by dissolving the dirt on the surface of your skin. As sweat and dirt mix with your body's natural oils, it can settle on your skin and breed bacteria. Bar soaps break this oily layer apart and lift pathogens away from your skin.
What is the most watched soap in the world? ›The most popular daytime TV soap is The Bold and The Beautiful (CBS, USA, 1987-current). According to the most recent statistics, the daytime drama - which is shown across 5 continents - gathered more than 24.5 million viewers worldwide in 2008. The Bold and The Beautiful has been winning this award since 2006.
What is best pH for soap? ›Majority of the soaps have a pH within the range of 9-10. Majority of the shampoos have a pH within the range of 6-7.
What oil makes the hardest soap? ›
Lathering hard oils include coconut oil, palm kernel oil, babassu oil, and murumuru butter. On the other hand, conditioning hard oils are oils and butters such as palm oil, cocoa butter, lard, tallow, kokum butter, illipe butter, sal butter, mango butter, and shea butter.
What is the hypothesis about soap? ›This is the hypothesis: If the type of soap is changed from liquid to bar, then the amount of time the soap will last will increase.
How has soap impacted society? ›The soap-like substance was used to remove dirt and grime from cloth and wool. Soap was actually used for laundering purposes for centuries, long before it was used for hygiene. The earliest civilizations cared less about hygiene in general, typically washing themselves in a river only when necessary.
What are the 5 uses of soap? ›...
5 Things To Do with Soap
- Prevent Cast Iron Marks. ...
- Deodorize Your Car. ...
- Mark a Hem. ...
- Keep Stored Clothes Fresh. ...
- Loosen Stuck Zippers.
Soaps have some major disadvantages over modern detergents:
Soaps react with metals (calcium, magnesium, iron etc.) that are dissolved in the water and form very insoluble precipitates (soap scum) that can deposit onto surfaces and are very hard to remove. Soap has lower solubility in cooler water.
Limitations of Soaps• Soaps do not wash well in hard water and does not form much lather or foam. The calcium magnesium or iron ions of hard water form an insoluble sticky grey coloured precipitate called scum which restricts the cleansing action of soap and makes washing more difficult.
What are the problems of soap? ›Soap isn't hard or long lasting. Soap feels slimy. Soap dries my skin out. Soap has weird orange or brown spots on it and/or smells bad.
What are three properties of soap? ›What are the properties of soap? Soaps are water-soluble, fatty acid sodium salts. Soaps are made of fats and oils, or they are fatty acids, using solid alkali (a base) to handle them. The most widely used process for making soap is the making of fats and oils.
What is the most important ingredient in soap? ›Water. Water is an essential ingredient. It's used to make a lye solution, which is combined with oil. The water helps the oil and lye complete the saponification process.
Which is the most sold soap in world? ›1-selling germ-protection soap. Since 1894, Lifebuoy has reached more than 1 billion people with hand hygiene education, helped redefine how millions of children learn the alphabet, and sold soap all over the world. Find out how this heritage brand continues to grow.
What is the oldest soap brand? ›
Pears transparent soap is a British brand of soap first produced and sold in 1807 by Andrew Pears, at a factory just off Oxford Street in London. It was the world's first mass-market translucent soap.
What is the longest running soap in the US? ›General Hospital is the longest-running serial produced in Hollywood, and the longest-running entertainment program in ABC television history. It holds the record for most Daytime Emmy Awards for Daytime Emmy Award for Outstanding Drama Series, with 14 wins.
Should you wash your bottom with soap? ›Good anal hygiene:
Don't use soaps as they will reduce the natural oils that protect the anus and may make the area dry and itchy. Use aqueous cream or a soap-free cleanser instead. Avoid vigorous wiping with toilet paper because this may cause further chafing of the skin, which can become inflamed or infected.
- The Seaweed Bath Co Energizing Body Wash.
- The Seaweed Bath Co Detox Purifying Body Wash.
- Jason Calming Lavender Body Wash.
- Alpine Provisions Castile Body Wash.
- Jason Purifying Tea Tree Body Wash.
- Weleda Citrus Refreshing Body Wash.
- SheaMoisture Coconut Hibiscus Body Wash.
While both bar soap and body wash work about the same when cleansing your skin, bar soaps eliminate the need for plastic packaging and typically last longer than your average bottle of body wash.
Are soaps losing popularity? ›From declining ratings across the board to Neighbours' cancellation and Days of our Lives' move to streaming only, soap operas are under threat like never before.
What is the healthiest soap in the world? ›- EcoRoots Organic Body Soap. ...
- Beekman 1802 - Bar Soap. ...
- Crate 61, Vegan Natural Bar Soap. ...
- Tom's of Maine Natural Beauty Bar Soap. ...
- Dr. ...
- Godai Handmade Soap Bars. ...
- 360Feel Men's Soap bar Handmade. ...
- Australian Botanical Soap, Goat's Milk & Soya Bean Oil Pure Plant Oil Soap.
EastEnders is the most awarded soap in the category, with eleven wins.
What pH is Dove soap? ›Dove soap is popular & is assumed to be gentle. It is a syndet bar rather than a true soap, meaning it has synthetic detergents, namely Isethionates. Its pH is around 6, which is much gentler on the acid mantle of the skin barrier than more common bars that range in pH of 9-10.
Is Dove soap acidic or alkaline? ›Dove, however, has a neutral pH that's balanced with your skin to avoid any damage. It actively cares for your skin, adding skin-natural nutrients to keep it feeling its healthy best.
Why is soap more effective than detergent? ›
The natural ingredients in soap have fats and glycerin that gently clean and moisturize the skin without causing irritation. While detergents need to add synthetic chemicals to moisturize or reduce irritation, the naturally occurring glycerin in soap makes the skin smooth and soft without additional chemicals.
What happens if you use soap everyday? ›“Frequent washing, particularly with soaps, strips natural oils from the skin barrier and increases water loss. This leads to drying of the skin and irritation,” he says. This can be a problem particularly for people with skin conditions such as eczema where the skin barrier is already impaired.
Is it healthier to not use soap? ›You don't need to use conventional soaps in your daily hygiene routine. All you absolutely need, bare bones, to stay clean is water. Just water. Water does a fine job of rinsing away dirt without stripping vital oils from your skin.