Cleansers can be divided into two main categories: bar or solid cleansers and liquid cleansers. Within each category are several subcategories of cleansers. This article will briefly discuss each subcategory and what characteristics define them.
Keep in mind that both categories of cleansers employ the same types of ingredients to do their bidding: emollients and surfactants. Emollients act as thickeners and temporary moisturizers, while surfactants actually cleanse the skin. They do so by reducing the tension between compounds that are more oil-soluble and those that are more water-soluble. How good a surfactant is at reducing this tension, is directly linked with its critical micelle concentration (CMC), which is the minimum concentration a surfactant needs to be present in order to form a micelle. Therefore, the lower the CMC of a surfactant is, the higher its potency.
While almost all true soaps are bar cleansers, many bar cleansers are not true soaps–something that a majority of the consumer population does not recognize. The distinguishing feature of true soaps is that they contain one or more forms of the alkyl carboxylate family of surfactants, such as sodium stearate and potassium myristate. These surfactants are created via a process known as saponification, where some type of triglyceride (derived from vegetable oil or animal fat) is reacted with an alkali (typically sodium or potassium hydroxide), to form hydrolyzed ester moieties or soap molecules. Due to the inherent alkalinity (as opposed to acidity) of these compounds, true soaps typically give a pH value of anywhere between 9 and 11.
For most people, while occasionally cleansing the skin with a true soap won’t be noticeably detrimental, regular use can result with excess dryness, redness, and inflammation–something that will be discussed in these posts (LINK).
Altered True Soaps
In attempts to tame the awesome drying and irritating aspects of true soaps, several more “sophisticated” versions were created. They include the following:
- Superfatted Soaps: By adding in more of the triglyceride content (mentioned above) during the saponification process and/or less of the alkali content, the relative triglyceride content will increase. This imparts extra emollience, which will increase hydration by reducing transepidermal water loss (TEWL), while suppressing lather, which in this case, is directly linked to a soap’s ability to “strip” the skin.
- Transparent Soaps: If you’ve ever used soap before, you’ll notice that it’s usually a creme or off-white color, if no colorants are added. So when I encountered my first “see-through” soap, I was like, “Whoa! How cool!” If you’ve ever been in that same position, now you’ll know how that happens. It’s quite simple actually. By including a high level of glycerin, which is both a humectant and an emollient, formulators are able to further solubilize and dilute the alkali surfactants, resulting in the trademark transparent appearance. These soaps tend to be more mild than superfatted soaps and have a softer and smoother texture.
- Combination Soaps: As the name suggests, these soaps contain a combination of the alkali-derived surfactants of true soaps, with the milder synthetic surfactants that are seen in liquid cleansers. While this is an admirable attempt to reduce efficacy, the potency of the alkali-derived surfactants nevertheless overpower their milder cousins, resulting in a mixture whose pH remains in the 9.0-9.5 range–something we DON’T want.
Synthetic Detergent Bars
Appropriately coined as “syndet bars,” these bar cleansers retain both the solid state of true soaps and the use of triglyceride-derived surfactants. However, syndet bars do not manipulate the latter via saponification. Instead, they rely on mechanisms such as sulfonation and ethoxylation. An example of ethoxylation is the synthesis of PEG-compounds by the addition of ethylene oxide. This process not only increases the water solubility of the original triglyceride content, which allows for easier mixing with water (obviously), it also reduces the potency of the originally harsh surfactants primarily by increasing the size of the interactive head groups (more on this later) with the addition of esters.
Fittingly, it is the manipulation of these interactive head groups that is responsible for the lack of soap scum when using syndet bars. Soap scum is actually caused by an ion exchange reaction between soap molecules (alkyl carboxylate surfactants) and common metal ions found in “hard” water such as calcium and magnesium; NOT by the soap itself. Try using soap with distilled water, and you’ll see that no tell-tale residue forms. But getting back on topic, when soap is dissolved in hard water, a precipitate is formed when the alkali metal ions (like sodium and potassium) are replaced with alkali earth metal ions (like calcium or magnesium). As these newly formed compounds are insoluble in water, soap scum forms. By changing the head groups to ones that do not bind with alkali earth metal ions, the “newer” surfactants used in syndet bars such as isethionates and sulfonates, are far less susceptible to forming soap scum.
Note that many of these “newer” types of surfactants are also used in liquid cleansers. And while every type of bar cleanser described so far exhibits a basic pH, syndet bars do not due to the absence of akali metals. Instead of giving a pH of ~9.0, syndet bars are characterized by a slightly acidic pH range of ~5.5-7.0.
These are all reasons why syndet bars, which exhibit a a lowered pH range and the presence of milder surfactants, allow for a more gentle cleansing experience than true soaps.
There’s not much to say about liquid cleansers. They are just like syndet bar cleansers, again utilizing both emollients and surfactants to do their dirty work. Literally! However, liquid cleansers contain a lot more water and are generally more varied in terms of what surfactants, emollients, and humectants can be used. This is because unlike with bar cleansers, formulators aren’t limited to choosing components that remain solid at room temperature, dry quickly after use, and do not absorb water and become mushy in a humid atmosphere. In some ways, formulating a bar cleanser is more difficult than doing so for a liquid cleanser!
But getting back on track, as stated liquid cleansers are much more diverse than bar cleansers. For example, it’s a lot easier to incorporate compounds that need to remain solubilized in order to function (such as glycolic acid and benzoyl peroxide in “acne” products) into a liquid cleanser, than a bar one. Furthermore, it’s a lot easier to manipulate liquid cleansers so that they give an acidic pH similar to that of healthy skin. However, keep in mind that liquid cleansers (and some syndet bars) that utilize soap (alkyl carboxylate surfactants), can retain a basic pH.
Other than emollients and humectants, which will discussed in the “Moisturizers” section (LINK), the primary characteristic that differentiates one liquid cleanser from another, is the choice of surfactants. They will be discussed next.
Note that many manufactured “oil” cleansers like the Clinique Take The Day Off Cleansing Oil and the MAC Cleanse Off Oil, are still technically liquid cleansers. While many people consider them to be in a separate category when compared to something like the Neutrogena Fresh Foaming Cleanser, they are essentially the same things. There are just higher amounts of emollients in these “oil” cleansers–something that’s good for longer-wearing formulas because they increase the solubility of any oil/makeup on the skin. But regardless, surfactants are still present to sweep everything away.
“Micellar” Water Cleansers
Similarly, “micellar” cleansing waters are also still considered liquid cleansers under our current definition. In the past few years, micellar cleansers have been all the rage with everyone from celebrity makeup artists to dermatologists claiming that they’re like nothing before seen. When in reality (and the gleeful manufacturers know this), they utilize the same two types of compounds to do their bidding: emollients and surfactants. The only difference that separates micellar cleansers from more traditional liquid cleansers, which also happens to be the same difference that separates any type of liquid cleanser from another, is the choice in surfactants and emollients, as well as how much of each is used. In order to remain like water, micellar cleansers use low amounts of water-soluble and lightweight emollients like glycerin, and low to high amount of surfactants that tend to be more gentle and exist as liquids at room temperature like the PEG-compounds mentioned above.
To demonstrate this, let’s examine the chief avatar of micellar cleansers: the Bioderma Sensibio H20.
Here is its ingredients list:
Water, PEG-6 Caprylic/Capric Glycerides, Propylene Glycol, Cucumis Sativus (Cucumber) Fruit Extract, Mannitol, Xylitol, Rhamnose, Fructooligosaccharides, Disodium Edta, Cetrimonium Bromide.
As you can see, this contains a decent amount of PEG-6 caprylic/capric glycerides, which is a synthetic surfactant that exists as a liquid at room temperature. It also contains a low amount of propylene glycol, which acts as the primary emollient (and solvent). Finally, there’s a tiny bit of cetrimonium bromide (a cationic surfactant), that acts more as a preservative than a cleansing agent.
So really, what’s so different about this? While it may exhibit a different tactile experience, it operates under the SAME principle as any other liquid cleanser. Think of micellar cleansers as the water-soluble portion of a dual-phase eye makeup remover. As only one half of their dual-phase counterpart, while most skin types can use them, micellar cleansers generally tend to be less effective at removing makeup. So micellar cleansers are certainly an option to consider. Just know that they’re not some breakthrough miracle product, unfortunately.
What’s the Best Type of Cleanser?
It’s no surprise that I champion liquid cleansers; they are the way to go. From cleansing milks to foaming washes and micellar waters, virtually everyone will find an appropriate option. Plus, liquid cleansers are also super easy to use. Just pump/squeeze and go. Syndet bars are another option, but I personally find them to be too messy and impractical to deal with on a regular basis. Clearly, true soaps should be ignored.
Finally, while I believe that surfactant-based liquid cleansers are the best option, some will undoubtedly inquire about the use of “natural” solutions like petrolatum (oh, the irony), cold creams, cleansing balms, or some type of non-fragrant plant oil like olive or jojoba oil. These types of products work under the premise of “like dissolves like.”
And it is a valid assertion. The applied oil will help loosen and soften the layer of oil on the skin, while the physical force of friction (as you rub this over the skin) will help emulsify that layer of oil. But therein lies the problem. You’re sitting or standing there with a doubly thick concoction of your facial oil and the cleansing oil on your skin, wondering how to remove it. You can try rinsing it off, which won’t help because water and oil don’t mix. You can also try wiping it off, which kind of defeats the purpose of using a “gentle” cleanser, since you’re repeatedly rubbing the skin in an attempt to remove all the oil. At the end of the day, you still need some kind of surfactant-based product (whether it’s a liquid cleanser or a wipe) to remove the oil. And you’ll have to use even more of it, since you’ve essentially added more oil.
I’m personally not a fan of this type of cleansing. It makes a one-step process into a two-step one. However, I admit that for certain purposes, these types of cleansers can be useful. For example, they can be great at dissolving waterproof mascara and eyeliner on and around the eye area. After rubbing the oil around for a while, the use of a surfactant-based cleanser can then easily and gently sweep everything away. Even then however, I’d recommend a good eye-makeup remover (almost all contain some type of surfactant already) and a cotton pad or washcloth instead. But hey, if that’s a way for you to save money or perhaps enjoy your cleansing routine more, go for it!