Updated: Jan 25
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What exactly is soap?
To best understand soap, it is good to first break down soaps by their main ingredients, what they do and what to look for.
Surfactants: The ‘workhorse’ of a soap. They are designed to specifically cleanse via degreasing.
Conditioning agents: In the process of removing oil from the skin or scalp, there are also agents meant to leave some hydration behind. Our skin is not ‘smooth’- it actually is ‘scaly’ with little grooves. Conditioning agents find their way into these grooves and attract moisture to them.
‘Special’ ingredients: These would be for specific concerns people are looking to address.
Miscellaneous: This is the category where I stick fragrances, preservatives, stabilizers, etc.
The “best” soaps recognize the role that the pH of the skin plays in protecting our skin from microbes in the environment. Our skin tends to be slightly acidic with a ph of less than 5. This protects us against microorganisms while also maintaining the barrier function skin is meant to play by avoiding the excess breakdown of lipids and natural oils in the skin.
What is the history of soap?
There is evidence of the use of soap as far back as almost 5000 years ago in Ancient Babylon, Rome and Greece perhaps used to clean skin and clothes. Archaeological and ancient finds seem to suggest that fat derived from cooking over flames mixed with ashes to produce the first types of soap. Lye is generally derived from water leached out of wood ashes.
Are all soaps the same?
As to what makes soaps different, the focus is on how each ingredient acts for better or worse.
Surfactants are polar particles where one end ‘likes’ oil and one end ‘likes’ water. The end that ‘likes’ oil attaches to the oil on the skin or hair like a magnet. This leaves the end of the particle that ‘likes’ water exposed. The exposed end of the surfactant that’s looking for water finds it readily in the bath or faucet and attaches like a magnet to the water. This pulls the oil off the skin or hair and rinses it away with the water.
There are some “aggressive” surfactants known as sodium laureth sulfate. Sulfates are something everyone loves to hate. They have been mislabeled as ‘bad’ for our health. The real issue when it comes to soaps and shampoos is that they are aggressive at removing oil and dirt. Sulfates are strong and cheap so they are an easy thing to add to products for their ability to clean. By leaving them out of baby soaps and shampoos, the product is less irritating to the eyes and skin. The trade-off may be that they are not as effective at cleaning.
The other category of ingredients that will likely vary from product to product are fragrances and some preservatives. Some fragrances have the potential to be irritating to the skin and eyes. Preservatives are important to some degree to avoid bacterial overgrowth in products but may be limited in baby soaps.
What are the different types of soap?
There are different ways to look at “types of soap” as there is no standard for distinguishing between the different types. Most soaps that are placed in a category are done so by the manufacturer for marketing purposes without a true standard that applies.
Most patients that inquire about soap ask about one of two breakdowns:
Liquid vs Bar Soap
Regular soap vs sensitive skin vs baby soap vs antibacterial
Liquid vs. Bar soap: Which is better for our skin?
From an effectiveness point of view, there is very little difference. Both kill microorganisms and both do so effectively. Both contain the basic ingredients required to clean.
Bar soap is historically the most common type of soap used but is somehow poorly understood. Some people think it could transfer bacteria onto the skin by touching it. Studies have shown that this is not likely true. Soap is technically “clean”. Even if a bar soap dries and bacteria find their way onto the bar, they are unlikely to be responsible for spreading disease. Once the bar soap is moistened with water, the surfactant action of the soap is “activated” and will manage these microbes.
Liquid soap is cosmetically more elegant and leaves less of a mess to use with easy dispensing. Liquid soaps, from an environmental point of view, are not generally well regarded compared to bar soap simply because they rely on synthetic ingredients and require more energy to produce. They also require a vehicle to dispense the product which is most commonly a plastic bottle which only adds to environmental waste.
What makes baby soap different?
Baby and adult soaps tend to differ based on the surfactant and miscellaneous categories. Baby soaps and shampoos tend to leave out one of the most “aggressive” surfactants known as sodium laureth sulfate. As mentioned earlier, they have been mislabeled as ‘bad’ for our health. The other category of ingredients that will likely be excluded from baby products are fragrances and some preservatives. Added fragrances can be irritating to the skin and eyes. Preservatives are important to some degree to avoid bacterial overgrowth in products but may be limited in baby soaps.
Can you briefly explain what parents should look for in baby soap?
I tend to ask parents to focus on “fragrance-free” when it comes to baby products. Fragrances are both irritating to the skin as well as sensitizing for the skin. This means that they can make our skin more sensitive in general. If a child already has a tendency towards eczema or atopic dermatitis, this can aggravate the condition.
Seeking “sulfate free” products or looking at the label for sodium laureth sulfate and avoiding these products.
I find that labeling for baby products is effective. Many companies that use the word “babies” on their packaging have taken these factors into consideration. They may have even reduced the concentration of these ingredients.
What makes certain soaps better for sensitive skin?
Sensitive skin soaps tend to pay close attention to the pH of the product trying to match the skin’s natural pH. Products with alkaline or high pH tend to impact the skin’s barrier function even in the absence of surfactants in the product. These products will also tend to focus on hydrating ingredients meant to be left behind to restore the skin after the surfactants have done their job.
What is antibacterial soap?
This is a topic that has gained a lot of attention in recent years when the FDA asked that manufacturers demonstrate an actual demonstrable efficacy of antibacterial soaps over regular soaps. The question is a good one. Soap does its job to clean.
Do we actually need to have an added antibacterial agent, usually triclosan in many brands, to add to its effectiveness to do so? There have been several studies that have shown that there is really little to no difference in the effectiveness of antibacterial soaps over regular soaps.
For day-to-day use, I encourage my patients to just stick with regular soap. Unless there is an underlying active pathology such as bacterial folliculitis or a pre-operative regimen necessitating the use of protocol designed to target bacteria for a particular purpose as designated by your physician, there is generally no need to get antibacterial soaps.
What are the essential elements that make up a bar or soap or liquid soap?
Bar soaps use lye (an alkali) to convert fats from animals and vegetables into soap which acts as a natural surfactant. Liquid soaps combine the basic components of soaps as listed above into a liquid product to serve a similar function.
Why are some soaps allergenic?
Soaps can be allergenic for two main reasons. The first is if the detergent quality of surfactants present is particularly harsh to the skin, the breakdown of the natural lipid layer of our skin will leave it open to environmental insults. The second is that if the pH of the soap does not effectively protect the skin’s “acid mantle” then our skin is left open to inflammation and risk for infection. The acid mantle is the skin’s method of maintaining a slightly acidic pH via a combination of natural oils and the skin’s natural bioflora.
How does soap clean?
Surfactants are polar particles where one end ‘likes’ oil and one end ‘likes’ water. The end that ‘likes’ oil is attached to the oil on the skin or hair like a magnet. This leaves the end of the particle that ‘likes’ water exposed. The exposed end of the surfactant that’s looking for water finds it readily in the bath or faucet and attaches like a magnet to the water. This pulls the oil off the skin or hair and rinses it away with the water.
How does soap ward off microbes?
Bacterial and viral pathogens are enveloped with a protective lipid layer. This lipid layer is precisely what surfactants attach to and then allow their hydrophilic portion to pull them away. The surfactant action of soap can both help the microorganisms wash away as well as destroy their lipid envelope breaking them down. There is a disruption in the chemical bonds holding them together allowing them to be pulled away from the skin and washed off as well as breaking them down into inactive particles.
Are there recipes for homemade soap?
As a disclaimer, I understand that there is a common tendency to think if we make personal products at home they must be better. I would have to argue that the inability to measure and control the pH of these products used on the skin can result in adverse outcomes. Manufacturers, especially long-established manufacturers tend to take this into consideration.
The basic ingredients for soap are
1. Fats: animal or vegetable
2. Distilled water
To add a fragrance or effect, essential oils can be added. To cosmetically improve the look of the product, colorants can also be added.