How Does Soap Work? What is Soap Made from? Why Should I avoid SLS?

July 16, 2018 5 min read


How does soap work? 

Chemically speaking, soaps have two ends and look kind of like a sewing pin: one end, the head, loves water (hydrophilic) and mixes well with water.  The other end, the tail can't bond with water (hydrophobic) but instead bonds with oil and grease. Soaps work to take grease and oil (fats) off of things because the tails chemically grab (bind to) the fats, and then the heads grab only water molecules, allowing the grease to be washed off, dissolved into water.  You can see this in action by putting some olive oil in a small mason jar along with some water.  Let it sit out on the counter for a few minutes and you'll see the oil clearly separated from the water-- they just won't mix-- no matter how hard you shake the jar, as soon as you stop, the oil and water will separate out again.  Now squeeze in some dish soap and shake again...TADA!!  The oil will bind with the soap and is now able to be mixed with the water.   This is what makes soap lather:  the water-hating ends of the soap molecules will grab anything that's not water, such as grease, or.. air!  The air bubbles will be swarmed with hydrophobic soap molecule tails, trapping them in water (bound to the water-loving soap molecule heads). This now leads us to ask...what ingredients are needed for soap to work?


What is soap made of? 

To make a soap we need to make a molecule that will have one end that loves water and one that loves fats.  Unsurprisingly, one of the main ingredients in soaps is some sort of fat! For hundreds of years, soaps were made from animal fats after an animal had been butchered:  tallow and lard.  This fat must be brought into contact with a strong alkaline (opposite of acidic) solution, such as lye,  to turn it into soap, a process called "saponification."  Our ancestors made lye by pouring hot water through hardwood ashes.  Today most soap makers still use lye; sodium or potassium hydroxide. Soaps that still have some fats or oils left as fats or oils in them after the reaction with lye will leave the skin feeling softer and smoother.


If you flip over a bar of soap or look at the label on many liquid "soaps," you'll probably see quite a long list of ingredients.  If soap is so simple to make and use, why are there so many ingredients? If you're wondering that, there is another question many will ask next. What are the ingredients in soap to avoid? Soap does not need foaming agents (SLS, SCS, SLES), antibacterial agents, or fragrance (artificial or natural). Soap only needs Lye (sodium hydroxide) and fat (oils) to do its job. Let's look at a few major types of ingredients and assess whether they are truly needed or even helpful: 

First, antibacterial agents (benzalkonium chloride, chloroxylenol, among others-- 19 have been banned by the FDA last year)  

Nowadays, many people assume that soaps somehow kill bacteria or "germs."-- or that they should.  But as we've discussed, soaps have always worked just by getting germs OFF whatever surface or material you wanted to clean and allowing water to wash them away. And that is sufficient- if the germs are off of whatever we want them off of, that surface is now clean. But recently "antibacterial soaps" have become popular-- these contain ingredients that don't just pull germs off our hands and down the drain, but rather are intended to kill germs on contact.  While such substances may have their place in laundering surgical tools or disinfecting food prep surfaces (though one could argue that peroxides and bleaches and UV light might work better in those settings, too), they are quite literal overkill on hands or bodies. 


Next, let's talk about "foaming agents."  

We've discussed why soaps lather, but because many people associate a lot of lather with a lot of cleaning power, many soaps have added ingredients to make them lather MORE.  One of the most common is "sodium laurel sulfate" or SLS. Unlike lye, which can be made fairly simply from natural ingredients, sodium laurel sulfate is a chemical which never occurs in nature. It makes soap foamier and can help dissolve dirt or grease in water (which soap already does on its own).  It's quite cheap to make.  Unfortunately, it is a skin irritant, and also has been linked to cancer, hormone disruption, organ toxicity, and neurotoxicity.  Since SLS doesn't really add anything to soaps that soaps don't do just fine on their own but does add risk, many consumers have begun to look for products without it.Which of course has led to many manufacturers using alternative names on their labels. soap-the-yellow-birdSLS may also be listed as sodium dodecyl sulfate, sulfuric acid, monododecyl ester, sodium salt, sodium salt sulfuric acid, sodium dodecyl sulfate, aquarex me or aquarex methy.  Related chemicals include sodium laureth sulfate, or SLES, which has a higher foaming ability and is slightly less irritating than SLS. Ammonium lauryl sulfate, or ALS, is similar to SLS and poses similar risks.  SLS is usually derived from petroleum oils, but can also be made from palm or coconut oils... which leads us to its trickiest alternative name:  sodium coco sulfate.  Just because the starting oil came from a coconut instead of petroleum doesn't make the finished chemical any more natural or less harmful (and testing will in fact show SLS as a large component of SCS).  Some companies will proudly label their products "SLS free!" but a look at their ingredient list will show sodium coco sulfate.  This is similar to claiming you make a "salt-free" burger when you in fact use a seasoning mix that contains salt.  Sure, you may use LESS salt because that seasoning mix isn't just salt, but you'll still have salt in your burger.  Similarly, using SCS may mean you have less SLS but you'll still have SLS in the product.


Lastly, many soaps will add in "fragrance."  

This isn't really a single ingredient but is a whole category of ingredients that the FDA doesn't require manufacturers to specify.  Unfortunately, most fragrances (scents) are artificial chemicals that are likely to cause many people to react.  While fragrances are inexpensive to obtain, they aren't needed in soaps because there are hundreds of completely natural herbs, flowers and other plants that have great scents.  Not only will these be less likely to cause an allergic reaction in people, they can be clearly labeled, allowing those who know they have a specific allergy or sensitivity to a particular plant or plant family to avoid products containing them.

If all of this information is overwhelming, never fear! All of our soaps are full of those skin healthy oils and FREE from all the "extra stuff" that hurts our skin. In fact, our Unscented Shea Soap is effective and incredibly pure, for even the most sensitive skin! 4 different oils and shea butter! You can't beat it! Check out all of our soaps(and all the other varieties are full of intentional, skin nourishing, botanical ingredients!) 

Nicole P
Nicole P

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