aren’t all the soaps antibacterial? How come some soaps (e.g. Dove) don’t mention anything about its antibacterial properties?
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Antibacterial means *kills* bacteria. And, at least in some jurisdictions, you need to actually to lab testing to prove that before you can make an anti-bacterial claim.
Removing bacteria (which all soaps can do) isn’t killing them, so doesn’t necessarily count.
All soaps have the property of weakening bacterial cell walls, and washing microbes off surfaces, but in terms of a legal definition they don’t hit that 99.9% kill rate that’s considered antibacterial. Soaps with additives such as triclosan and the like do generally kill at a much higher rate, but they come with their own issues such as breeding resistance in the surviving populations of microbes.
So in practice anti-bacterial soap is regular soap with one of these additives specifically designed to be antimicrobial. Such additives might also leave a residue that has the property of temporarily halting bacterial growth, so-called bacteriostatic action.
Yes, soaps are inherently antibacterial. They can disrupt the cell membranes of bacteria, which kills them. I’m not sure of the statistics there on % killed as a function of time, but you do need some contact time to see a big reduction.
Some soaps add one or more ingredients specifically to target killing bacteria. I think the presumption is that they’ll kill of a higher percent at shorter contact time, although I believe the evidence for that is shaky at best.
Washing your hands with soap *does* kill bacteria present, however that doesn’t make the soap antibacterial. Soap works by forming a complex with the plasma membrane of germs, and ripping them open as you add mechanical action and friction. This works for all germs, and is not something pathogens can build an immunity to!
Antibacterial means that if you apply soap directly to the germs, like on a petri dish, it will kill the germs or stop them from growing. Soap does not do this, as you need a lather composed of soap and water plus the mechanical action I mentioned previously to cause the membranes to rupture. This is why soaps sanitize things but are not antibacterial!
It’s marketing trick. Post and amid Corona pandemic I’ve been noticing a lot of of soaps are now labeled ‘antibacterial’. Previous not so much.
Your greasy hands are covered with oil that is naturally secreted from your skin. That oil protects your skin but also traps dirt and germs. The main function of soap is to wash away that dirty oil layer, and thus also wash away dirt and germ, bacteria, viruses, you name it. Soap naturally can also kill some germs, but that takes time, because penetration though the cell wall takes time. But its main function still is to remove the unwanted.
So soap is a great invention that is so basic and simple in its ingredient, but does its job really well. For lay people and greedy corporate men, that’s apparently not enough. Now they add some ingredients are known having bacteria-killing or bacteria-deactivating properties like Triclosan for example to the soap and PR that as the better soap. Because if the product is the same as the competitors, it won’t sell.
But little they know that that ingredient albeit can somewhat kill the bacteria in your 20 second hand washing session, it can also f*k your endocrine system up, and do many side-effect dumb things, also bring a risk of introducing new kind of drug resistant bacteria. The end-effect of using antibacterial soap is unknown, compared to normal soap.
It’s all about marketing and tricking the consumers.
There are basically two ways that we can kill bacteria with chemicals.
The obvious way is by introducing a chemical that physically damages the cell. High concentrations of salt or alcohol will pull all the water out of cells and kill them. Soap will dissolve cell membranes and kill them. From that perspective, all soaps are “antibacterial.”
The other way is to take advantage of “programmed cell death”. Many cells (including many bacteria) have a mechanism to self-destruct when they get the proper signal. That’s “normally” invoked when killing off some cells is beneficial to the larger community of cells. “Antibiotics” trick cells by sending those signals. The problem is that cells eventually “learn” to ignore them. (“Learn” is actually total BS here. What’s actually happening is that not all cells pay attention to the kill signal reliably and when all the other ones die out the population evolves to one that consists entirely of bacteria that ignore the kill signal. But it looks like learning at the population level)
Typically a soap labeled “anti-bacterial” will have some amount of the latter chemicals in it.
Soap is a high ph chemical like bleach that will kill/inactivate most types of bacteria and enveloped viruses (which includes flus, most colds, and coronas). Different microbes are vulnerable to different chemicals; for example, low ph chemicals like citric acid work well on most enveloped viruses but not the type of nonenveloped viruses designed to withstand stomach acid. I believe the WHO recommends hydrogen peroxide added to homemade (for impoverished 3rd world areas) alcohol based hand sanitizers for bacterial spores. I like hand sanitizer with CHG as it binds to the hands with washing off from water for 4+hours for residual killing/inactivating activity. Presumably some soaps (and hand sanitizers) add additional chemicals to get their kill ratio up.
Certain metals like silver and copper will kill anything due to their release of ions that perforate microbes.
Hands are porous and have a slightly acidic ph which makes them mildly antimicrobial and, unless you regularly pick your nose, contact transmission of many pathogens wont survive long and are more of a threat via other routes.
There are a class of compounds called ‘surfactants’ that have an end of the molecule that dissolves in water while the other end dissolves in oil. Soaps and detergents are two different ways of making surfactants.
Living things also use surfactants to separate the inside of the cell and the outside. These are called phospholipids.
Phospholipids arrange themselves in a layer called the cell membrane. That works in water. If you add another surfactant the phospholipids stop being a layer. Since that layer is like the ‘skin’ of the cell, disrupting the skin kills the cell.
Some cells have structures that makes it so that the soap or detergent can’t disrupt their cell membrane. They aren’t as easily killed by soaps and detergents.
Yes, all soaps can clean dirt and bacteria away but there’s an extra ingredient in some not found in soaps like Caress. Also, Dove markets exclusively to women. Stronger antibacterial soaps throw off the pH and ‘lady’ environment if left there too long. From a marketing standpoint, why bother getting blamed should women leave it down there longer, trusting Dove promoted as gentle and get yeast infections? Ivory is pure, not gentle but common sense is there to rinse. Irish Spring’s for grown men, so is Dial. Pretty rough soaps…
The basic principle of how a soap works is that it dislodges foreign bodies from the surface it’s applied on, and then rubbed in, very important, so that they’re suspended in the soap instead of stuck on your skin, or surface you’re cleaning, and they are then washed away along with the soap.
However in practice this is not a perfect process, and soap can’t get anything and everything off. Some things remain on the surface, even if it’s imperceptible to us. Also it might not just be your hands or skin you’re washing but a surface or an appliance. Maybe you’re cleaning with a rag or sponge and just as you’re wiping the dirt and bacteria away you’re putting some back onto the table with the next swipe. So since getting literally everything off is impossible, the next best thing is to have antibacterial soaps which not only wash away bacteria, microbes and the like but also kill them, so even those that may remain are actually dead and not harmful any more.
Of course most soaps out there are also antibacterial soaps nowadays, it’s just that in order to be able to be branded as such they have to have a disinfection rate above a certain benchmark.
Then again not all soaps are antibacterial. For example car soaps do a great job of breaking down and removing the dirt you’ll commonly find in cars, like mud, and debris mixed in with grease or oil or fuel. But they’re not antibacterial, since well their job is to remove the dirt from the car not make it suitable to eat off of.
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