Bar Soap vs Body Wash: Does pH matter?

August 20, 2026

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What is Soap?
The Importance (or not) of pH
Marketing vs. Reality
Handmade vs. Commercial Soap
More Important Than pH

Do you use soap or body wash in the shower? Well, unless this post has circulated farther from the Fat Chance Soap world than usual, my guess is you're more likely to use soap. Though from anecdotal evidence at least, I would guess that more people use body wash than ever before, especially millennial and younger generations.

You know I'm not a big fan of anecdotal evidence and I'd love to give you some hard statistics on soap vs. body wash preferences but the most recent publicly available survey is from 2016, which is already ten years ago. Trends in opinion surveys change quickly enough that I don't think it's worth spending time picking apart old data!

Marketing has a lot to do with the choices people make and a popular one that I see in advertising is products that are "pH balanced," which we are told is a positive quality that is better for the skin. Before we get into that, though, let's figure out what the difference in between soap and body wash. Despite the terms often being used interchangeably, there is a difference between them.

What is Soap?

Soap is made out of saponified fats and oils. The ingredients list in a soap product with either contain lye/sodium hydroxide or it will list the ingredients as they are after reacting with the lye, following the format of "sodium _____ate" depending on the type of fat or oil. Some examples are sodium tallowate, sodium cocoate, and sodium palmate. Most laundry "soaps" and dish "soaps" contain zero soap. This is just a language shortcut people use or perhaps a linguistic leftover from back in the days when these products were in fact soaps.

If it's meant for cleaning but isn't actually soap, than it is likely made from a variety of detergents. Unlike soap, detergents are not easily made in a home or DIY environment. Manufacturing detergents requires industrial equipment housed in dedicated manufacturing spaces. It is possible to buy premade surfactants for mixing at home but with the need for grinding equipment, dealing with high melting points, and more complicated recipe formulation it's still rather more challenging than soap.

For products meant to clean skin, you can use soap or body wash ("shower gel" is just another type of body wash, often with fewer moisturizing ingredients). Both of these products can be either solid or liquid, so you'll need to look at the label to know which is which. For the purposes of this article, if it's made with soap, I'm calling it soap, if it's made with synthetic detergents, I'm calling it body wash.

Does the difference even matter?

Soap and body wash both perform the same job, they get you clean! They also both use surfactants to do it. A surfactant is a compound that reduces surface tension to facilitate mixing of two components that don't typically want to mix. In the case of cleaning your skin, surfactants allow water to mix with the dirt and oils on your skin on a molecular level, so they can be washed down the drain.

The importance (or not) of pH

The pH scale is a measure of how acidic or basic/alkaline something is. The scale ranges from 1 to 14, with 1 being highly acidic, 7 being neutral and 14 being highly alkaline. Healthy human skin is mildly acidic and measures between 4.0 and 6.0 on the pH scale.* This pH fosters a healthy population of beneficial skin bacteria and helps maintain the integrity of the skin barrier.

*Technically, skin is a solid and only solutions (i.e. liquids) can have a pH. When we say that the skin has a pH, what we're actually reporting is the pH of the top layer of "acid mantel" when mixed with neutral water.

Red indicates the acid range, blue the alkaline range, 7 is neutral. Please enjoy my handcrafted graphic design

By necessity, soap is alkaline, usually with pH between 9 and 11. If you try to make the pH more acidic, the compounds that make up soap will start to break down and you'll end up with a gooey mess. So if you see a "soap" product advertising that it is "pH balanced" or somehow "matches the pH of your skin", it's definitely not soap and is most likely a body wash.

The detergents in body washes on the other hand, can operate effectively at the more acidic end of the pH scale. (This is also true of shampoos and conditioners, which also rarely contain actual soap and instead use detergents). The detergents used to make them usually operate best at a slightly acidic pH and during manufacturing, the actual pH of the product is tested and adjusted to keep it in that optimal range.

There is a small exception to rule of "sodium hydroxide on label = soap". Sometimes sodium hydroxide (lye) is used as an alkaline pH adjuster, which means in some products you might see it listed way at the end of ingredient list (since it's used in very small amounts), while in actual soap, lye is typically listed right after the fats/oils and water (or other liquid).

Marketing vs. Reality

The marketing departments of body care products have really taken this pH thing and run with it. If healthy skin has an acidic pH, then every single product you put on it should match the pH of your skin, right? I'm especially suspicious since the products trying to convince us that "pH balanced" is the be all and end all of body products are typically higher end brands charging a premium for their products.

So, if you're accustomed to always taking marketing claims with a grain of salt, you're probably thinking that we've skipped a step here... We know the pH of the skin and we know the pH of soap and body wash but has anyone actually tested if your skin's pH is affected by these products?

Testing skin pH

Well, it's happened at least this once. This 2014 study tested the skin pH of two groups of people, those who used an alkaline soap-based cleanser for more than 5 years and those who used a mild-acidic cleanser for more than 5 years. The skin on their forearms was pH tested before washing, immediately after washing and then 6 hours after washing.

The result? No change in skin pH, regardless of the cleanser used.

Testing skin water loss

A study from 2021 measured "transepidermal water loss" (TEWL) in two groups of subjects who used either a low pH (5.5) "skin identical" cleansing bar or a neutral pH (7) cleansing bar. Neither of these products were true soap, rather the study was trying to see if matching the skin pH was beneficial to the skin barrier.

It turns out that the neutral pH cleanser caused less TEWL than the "skin identical" acidic one. They determined that this result was because the skin barrier was more affected by how the cleansers interacted with the skin rather than just straight pH. They theorized that the presence of emollients and moisturizers was likely far more important than hitting a certain pH number when choosing a cleanser.

Citing Studies Without Understanding Them

I won't use either of these studies to completely exonerate soap or as a reason to insist that pH is clearly unimportant but it does make me pause before fully embracing the "skin identical pH in body products is essential for skin health" theory.

It's very popular right now, especially if you want to be taken seriously with "research style" writing like this, to "do your own research" and cite scientific studies that prove your point. The issue with this is that scientific concepts and hypotheses aren't proven by single studies. Humans are fallible and individual studies are only one data point. To really prove something, other scientists must be able to repeat your study and get similar results. The results should demonstrate how and why something works, or at least contribute to the understanding of the concept.

Unfortunately, soap and cosmetics just don't attract a lot of independent research. I think the reality is that there's just not a lot of career building credibility to be found in doing studies on the next great shampoo ingredient or the next great lotion formula. That kind of research is very appealing to brands to help them design new products but that research will be done in house by their own employees, so they aren't giving away their next big recipe to the competition.

Since we don't have a large body of work to look at, we risk cherry picking only the studies that support our argument, which is not unbiased research. These kind of quirky study results have been making headlines for decades and when a few months or years later when somebody says, "oh wait, actually we couldn't repeat the results from that study because it was poorly designed!", the public is no longer paying attention.

So my best option for staying at least somewhat unbiased for this post was looking at a lot of articles arguing against soap and followed their citations. What I found was a lot of studies that weren't any more definitive than the two vaguely "pro-soap" studies I cited above. Some of the more blatantly "anti-soap" studies are not actually "studies" that ran any kind of actual experiment.

This paper, for example, has a lot of good information about the chemistry of different cleansers and the biology of the skin. However it immediately makes the leap that since skin has an acidic pH and soap and alkaline pH, soap is bad for your skin. They made this assumption without testing it, giving citations for other papers which also did not test this assumption.

Other studies using "patch tests" put soap on a participant's skin and then leave it there for hours. No surprise that this caused irritation and raised skin pH in a lot of people, since that's not how you're supposed to use soap.

There are other studies that find a modest increase in skin pH after using soap for washing and that increase was indeed more significant than washing with water or an acidic cleanser but they still failed to show that this increase led to irritation or that it lasted any significant amount of time. And while the increase was statistically significant, it was still small. Especially when compared to the fact that washing with any kind of cleanser or even just plain water also raises skin pH a bit.

Then there are the studies that show significant irritation from soap but these are looking at healthcare workers who may wash their hands 10 times a day or more plus hand sanitizer use. Anyone who uses soap this often is going to see irritation unless they are very on top of their moisturizing game. (Indeed, most of these studies were testing which emollients work best for health care workers, not the ideal pH of a cleanser). This type of study is not very relevant to someone wondering which cleanser to use in the shower once a day or to use occasionally on their hands.

Handmade vs. Commercial Soap

It is vitally important to note, that handmade soap and commercial soap are very different beasts. When fats, oils, lye and water are combined, the saponification (soap making) reaction begins. The soap that results is very rich in glycerin, which is a powerful humectant. Humectants attract water from the air and draw it into the skin, which makes glycerin a powerful moisturizer.

Glycerin is also a valuable product used in many cosmetic and industrial applications. It can be extracted from soap with an industrial process and then used in other products by that same company or sold at a profit elsewhere. The soap left behind is still perfectly good soap, in fact its shelf life is even increased a bit, but it is far less moisturizing than soap with the glycerin left in.

So you can imagine that the soap used in any study looking at skin irritation or dryness is almost certainly commercial soap, which means it is already going to be more drying than handmade soap due to the lack of glycerin.

More Important Than pH

If I've learned one thing from writing this, it's that the pH of cleansers seems to be more important to body wash and soap marketing departments than it is to scientists. Since there doesn't seem to be a conclusive body of research that definitively tells us that soap is great or that soap is horrible, I'm inclined to fall back on personal and customer experience. That experience tells me that there are many things that have far more impact on your skin than the pH of your cleanser.

Water Temperature

Hot water is more drying to your skin than cooler water. Combine that with a cleanser (body wash, soap or whatever) that is full of surfactants looking to clean up oils and you have a recipe for dry skin. All cleansers, no matter their pH are more effective in hot water, so the hotter your shower, the more of your skin's oils will be washed away. So if you're struggling with irritation and dryness, try cooling your shower down a bit. I'm no masochist looking to convert people to ice cold showers but there's sure to be a happy middle ground that neither gives you hypothermia nor boils all the oils out of your skin on the regular!

Bathing Frequency

This may sound funny coming from a soap maker but many people probably use soap or another cleanser too often. For most people, the grime of daily life can be easily showered off with just water or you can at least limit your use of a cleanser to the more vital areas of pits and groin. Many studies that I looked at seemed to indicate that healthy skin is able to bounce back from changes in pH pretty readily within hours of bathing (how many hours? 6? 14? 0? depends on who you ask). If you have easily irritated skin however, it makes sense to me that perhaps your skin has a little more trouble maintaining its balance, so the less it has to constantly recover from cleansers, the better.

Moisturizing

My big takeaway from all the studies of healthcare workers that I looked at, is that moisturizing is much more important than cleanser choice for keeping a healthy skin moisture barrier. Especially in a situation like health care where you have very little choice about how often you wash your hands, supporting skin with lotion and moisturizer is vital. So if you do have to wash your hands a lot or you simply can't give up daily, boiling hot showers (no judgement, I know they feel great!) then adding moisture may be your best bet.

The Soap vs. Body Wash Debate

pH isn't the only element of this debate. Whether to use soap or not stretches into environmental issues, hygiene and even the value of small businesses. I'm going to make this into an informal series of posts addressing more of these points, so look out for future installments!