Saturday, April 21, 2012

Chemistry of our skin: pH and our skin care products

As we saw yesterday, the pH of our skin is pretty important. Out of whack pH levels can lead to an increase in scaling, a decrease in hydration, and a possible increase in bacterial and yeast infections. In short, having an out of whack pH level can lead to dry skin and icky infections! (And I mean way out of whack! Here's a post on that topic, but the quick summary is that anyone who claims to have alkaline skin must be suffering from infections and incredibly dry skin!)

Does this mean we should care about the pH of the products we use? In this study, the researchers formulated three oil-in-water lotions with different pH levels, A had a pH of 3, B had a pH of 5, and C had a pH of 8. Here are the results....
Alkaline pH of the skin care products induced the disturbed barrier function. The TEWL (transepidermal water loss) of the SC (stratum corneum) was measured to investigate whether or not the skin barrier function was altered by applying the different pH skin care products. After 2 weeks, A (pH 3) reduced the TEWL of the SC significantly after application. After 5 weeks, C (pH 8) increased the TEWL of the SC significantly in comparison with other skin sites...So this implies that long-term application of alkaline skin care products can alter the SC barrier function more than acidic cosmetic products...Skin colour, water content and UV response was not altered by pH of the applied skin care products.

In our study, the alkaline skin care product impaired the skin barrier function after repeated application over 5-week periods. So, TEWL was increased significantly and the single 24-h exposure to 1% SLS impaired significantly the skin barrier in comparison with acidic cosmetic product. Our results demonstrated that the skin barrier was disrupted severely by SLS-induced irritation because SC was already impaired by alkaline pH and sensitive to external stress. So, this implied that pH of the skin care product we use daily is very important for the skin barrier, homeostasis and sensitivity. (From this paper)

This study concluded that using a leave on product with an alkaline pH was a really bad idea that could lead to an increase in transepidermal water loss, which we know can increase the feeling of dry skin! 

What does this mean for alkaline products, like cold process soap? 
Here, we have demonstrated the importance of the electrostatic interaction by showing that the pH of the skin surface has important consequences for the binding of resident bacteria on the skin, i.e. under acidic conditions the dispersal rates of endogenous bacteria are much lower than under alkaline conditions...The exact mechanism, which may explain these differences in dispersal rates of resident flora, is not known. It is suggested, that under alkaline conditions both the keratins, which constitute the corneocyte, and the bacterial surfaces are negatively charged resulting in repulsion. The role of the lipid-cornified envelope in adhesion of bacteria and the binding to sugar-containing receptors, would be less important under these conditions. Another factor, which may explain the enhanced dissociation of skin bacteria, is the high swelling of the skin under alkaline conditions due to the high netto negative charge of the keratins; this may open up the ‘sponge’-like corneocytes, allowing the bacteria to diffuse to the surface. This explains not only the higher numbers of bacteria detaching from the skin at alkaline conditions, but also the fact that repeated washings hardly show diminished numbers of bacteria; apparently, the resident skin bacteria are located even at relatively deep layers in the SC of the skin. 

It is well known that washing the hands with conventional alkaline soap will liberate large amounts of skin bacteria; this can easily be visualized by pressing the fingers on agar-plates after washing and subsequently count the colonies after breeding. Repeated washings (up to 10 times) fail to reduce these numbers of bacteria. This is why in hospitals the intensive washing of the hands before operations has been questioned. (This paper. Conclusion.)

If you want to get rid of bacteria, you really want something alkaline to detach them from the skin. (I really encourage you to read this paper as it goes into the beneficial and detrimental bacteria we find on our skin! It's so interesting!)

And take a look at this...
INTRODUCTION: Initially linked to antimicrobial function, the acidic skin pH plays a key role in permeability barrier homeostasis and integrity of the stratum corneum. Barrier recovery is delayed when acutely perturbed skin sites are exposed to a neutral pH. 
OBJECTIVE: To evaluate the pH of commercially available rinse-off products in Sri Lanka, and the effect of detergent rinses on skin pH and its recovery rate. 
METHODS: The pH of 18 rinse-off products was determined using pH indicator paper and a pH meter. The effect of an alkaline (pH 9) and an acid (pH 5.5) rinse-off product on the hand skin pH was compared in 48 healthy volunteers after single and multiple applications. The skin pH of the dorsum of hands was measured in nurses before (n = 131) and during (n = 40) a duty shift that involved frequent hand washing using alkaline soap. 
RESULTS: Soaps available in Sri Lanka have a pH of 9.1-10.5. The pH of syndets and cleansers range from 5.5-7.0. Five minutes after hand washing, the mean skin pH increased by 1.7 +/- SD 0.5 pH units with alkaline soap, and by 0.8 +/- SD 0.4 pH units with acidic cleanser (p < 0.0001). Recovery of pH was slower when alkaline soap was used. The increase in skin pH was significantly greater when hands were repetitively washed with alkaline soap (p < 0.0001). The mean skin pH values of nurses before (4.9 +/- SD 0.4) and during (5.7 +/- SD 0.7) the work shift were significantly different (p < 0.0001).
CONCLUSIONS: Alkalinisation with rinse-off products increases the skin pH with potential functional and clinical implications.
Citation: Gunathilake, H., Sirimanna, G., & Schurer, N. (2007). The pH of commercially available rinse-off products in Sri Lanka and their effect on skin pH. Ceylon Medical Journal, 52(4), 125-129.

...recent studies show that high-pH solutions, even in the absence of surfactants, can increase stratum corneum swelling and alter lipid rigidity, which suggests that cleansers with a neutral or acidic pH close to the normal pH of 5.5 are potentially less damaging to the skin. (This paper.)

I keep encountering study after study that shows that using an alkaline product for any length of time can result in a higher pH or dry skin. In this post on humectants, we saw that we don't want the lipids in our stratum corneum to be rigid as it can lead to dry skin. "The solid system produced with an all-saturated fatty acid mixture causes an extreme water loss due to breaks in the solid crystal phase." So again, using products that aren't in the pH range our skin wants can lead to dry skin.

Using something incredibly alkaline - like hair relaxers with a pH of 11 to 13.6 - can result in a change so dramatic that irritation and inflammation can occur, and you can end up with wounds. (Innate Immune System of Skin & Oral Mucosa). But this is an extreme example!

So what does this mean for alkaline products, like CP soap? It'll get rid of bacteria really well, which is awesome. And those of you who make CP soap know all about superfatting, which ensures that there is more moisturizing power in your soap than a soap without the superfatting.

I need to make this point clearly - I'm not saying anything against CP soap from a personal experience. I love CP soap, and I buy good stuff made by great soap makers because I find it quite lovely for my skin. I know that the studies I've posted are advising against alkaline products, and CP soap is an alkaline product, and this is making people upset. I'm just posting what I've found. You might have personal experiences in which CP soap has helped your friends or family with skin problems, and I don't want to negate those experiences, so I'm having trouble reconciling the studies I'm seeing - and there are more than I've posted here - with our experiences with CP soap. I like hearing your experiences, but anecdotes don't make science. Posting that your friend loves your soap or that your mom benefitted from something you made or that your dad is doing well with your soap is your experience, but it doesn't constitute scientific fact. I'm not sure what else to say here. I didn't expect to come upon these findings and I don't know how to interpret them because I know it's upsetting people. I'm not sure how to end this paragraph, so I'll just end it with a few periods...

And what does this mean for people with dry skin? Acidic products are your friend, and making your products more acidic is a good thing. I realize this might seem counter intuitive, but adding something like an AHA can actually help your skin trap water better!

Join me tomorrow as we take a look at more dry skin facial products! 


melian1 said...

so i've been thinking about this deal where folks skin improves using cp soap. it happened to me also. purchased soap left my skin painful it was so dry and troubled. my own cp soap (with superfatting) was so much better.

i wonder if it has got more to do with the particular oils used, the superfatting, and such than it does with alkaline cp soap being good for the skin? commercial soap is akaline also, so mere alkalinity can't be the answer.

i'm thinking that the less harsh handmade cp soap, plus the superfatting and the oils used is why the skin reacts so much better to cp soap than commercial.

i also wonder if after using the cp soap if we tried applying something acidic, like an after-shower spray or lotion or some such, if that would help the skin pH recover quickly and improve the skin even more.

Soap Lady said...

As an Aesthetician and soapmaker,I have always followed the golden rule of skin care which is "A Cleanser is always followed by a Toner" The toner removes a excess cleanser and restores the skins pH. Body toners have been used in spa's for years and at home our lotions are the substitute for toners. I adore cp soaps and shower
gels and would never stop making and using them, so I simply acidify the skin after use to assist the skin which by the way will (depending on your age) revert to its acid pH within a few hours. At the end of the day product making is a science, and a little knowledge can go a long way in helping us product a beneficial product. Just my very long two cents.
P.S. Susan, Love,Love your blog.

Clive said...

Very interesting blog post. Since I began making (and using, of course) CP soap I have found that my skin is definitely better than when I was using Dove (a syndet bar). However my early experiments with body washes using amphoteric surfactants and a pH of 6, seem to indicate that those are even better. There is no glycerine in syndet bars; could that be the only cause of the difference between commercial and cp soap?

Lise M Andersen said...

Absolulely excellent post Susan. I siply must pin this one! :)

Lise M Andersen said...

arggh!! Couldn't pin it due to no pics... Still love it though!

Will said...

Well, I was coming here for a light read and holy stuff am I feeling a brain overload.

I'm a CP-maker, unquestionably surprised by the info, and I'm thinking I need to print this stuff out and start reading when my brain is fresh.

Thanks for the news and info.


Caroline said...

I had a couple of chemical peelings about 2 years ago. And what I had to use after the treatment, as much as I wanted, was a acidic cream.
Your post explains perfectly why this is necessary after such treatments as my skin had to recover from all the damage that was done.
Bravo for explaining this.

Terri said...

Love this post. I have super-dry skin, and I have tried both CP soaps and syndet bars. My skin improved significantly when I started using the Ridiculously Moisturizing Body Wash with SCI and Esters recipe a few weeks ago. I know the moisturizers and humectants in the recipe help, but I suspect it also leaves my skin in a more naturally acidic state, which improves barrier function and reduces TEWL. Thanks for sharing this information.

zaczarowany pierniczek said...

Great post Susan!

"i wonder if it has got more to do with the particular oils used, the superfatting, and such than it does with alkaline cp soap being good for the skin? commercial soap is akaline also, so mere alkalinity can't be the answer"

I've read in some cosmetic dermatology books that different fatty materials used in detergents and soaps make a difference indeed. Apparently those based on coconut oil (especially lauric acid) are the worst in terms of irritation and removing both lipids and NMF compounds from the skin. So the longer chain fatty acid the better...if I remember correctly :P

Anonymous said...

Hi Susan, you mentioned it was hard to find cetyl esters. I found them at ingredients to die for in case you or anyone is interested in those. Good price too.

OllieBlue said...

These studies are very interesting - thank you Susan. 
As a non-scientific person I can only add my experience and musings. 
Water itself is also a higher pH than that of skin and when I had extreme dryness, was advised to use lotion to cleanse my body, and avoid water. Or, at best, to slather myself in oil based lotions (e45) before getting into the shower. 
So, whether using syndet or cp soap, we are still cleansing with water, a higher pH. 
The differences are the removal of bacteria, which, if left on the skin might do more damage (another subject and study), and with cp soap, glycerin and oils. 
As normal, healthy skin recovers its pH - after all, these cleansers and water are in temporary contact with the skin - perhaps it is these extra conditioning factors that make cp soap so much better feeling than syndets. And again, it does disperse bacteria which pH 'friendly' syndets do not. 
If our skin is getting dryer and dryer, and not recovering its pH quickly enough, should we be cleansing with  water at all, let alone syndets or soaps?  Perhaps 'washing' with oil is a better option, wiping away the bacteria as best one can. 

Anonymous said...

On February 24, 2013 at 2:15 pm

I am very interested in finding out more about what anonymous said. I notice what they
Posted makes so much sense. Do you have any suggestion on what would be a good nonirritant alkali wash.

Anonymous said... Very interesting reading but one major flaw. It has baffled me for years how 'scientists' forget the science. Skin does not have a pH as it is not soluble. The measurements are taken from the secretions of the skin. The skin, our biggest organ, has a duty to excrete toxins from our bodies and these toxins are acidic. With this in mind why would we want to wash acid with acid? Washing with an alkali removes the acid toxins and allows us to clean with the minimal of ingredients. It is the pH buffers and preservatives in acid syndets that are irritants.

Susan Barclay-Nichols said...

Please don't post as anonymous. I asked you - my readers - to attach a name to your comments as it offers a greater sense of community and it reduces the incidents of mean-ness. Future comments in this thread without names will be deleted. Just sign off with your name and let us know who you are!

What you say is quite interesting, and I will ask you to back up your assertions with evidence from reputable sources as I have done in this post and others. (EWG, Skin Deep, and the Suzuki Foundation are not considered reputable sources.) "Extraordinary claims require extraordinary evidence", so I will expect some awesome citations with links!

Can I be honest here? I am always a little worred when someone puts the words scientists or science in quotes. Why the quotation marks? It feels really insulting. ( I am not a scientist, but I do have great respect for those who have devoted their lives the pursuit of it.) Let's not put others down!

Susan Barclay-Nichols said...

I haven't heard from you, Anonymous, and I'm a little disappointed as I was looking forward to seeing your response.

It isn't logical to think that we would use an alkaline ingredient on our skin because our goal isn't to neutralize the acidic nature of our skin. Our goal is to clean or moisturize or do something else to it. Neutralizing the pH would do some serious damage to our skin. I wrote about this a while ago, but it would be very dangerous to have skin that was neutral or alkaline.

I have written a post with some information that might interest you here - Chemistry Thursday on Friday. Let's talk more!

Heather Wall said...

"Anonymous said...
Very interesting reading but one major flaw.
It has baffled me for years how 'scientists' forget the science. Skin does not have a pH as it is not soluble.
The measurements are taken from the secretions of the skin. The skin, our biggest organ, has a duty to excrete toxins from our bodies and these toxins are acidic.
With this in mind why would we want to wash acid with acid?
Washing with an alkali removes the acid toxins and allows us to clean with the minimal of ingredients.
It is the pH buffers and preservatives in acid syndets that are irritants.

February 24, 2013 at 2:15 PM"

I am not a scientist (yet) but I'm pretty sure that not everything your skin secretes is a toxin. The acid on your skin is a barrier that protects it from toxins, pollutants, fungus, etc. if you destroy that barrier by constantly bombarding it with alkaline products then you destroy what was naturally meant to protect you. Saying scientists forgot the science is this comment is kind of ironic.

Skeeter said...

In reference to the body exuding acidic body fluids, I have an older book, "Folk Medicine" by D.C. Jarvis, M.D. In this book, Dr Jarvis discusses some of his medical studies to the people in rural Vermont, USA. In particular, he mentions our health and the importance of our body fluids being within an acidic range. He speaks of occasions when our body fluids may shift to the alkaline range and how that indicates certain unhealthy conditions. He tested this theory. His results initiated his recommendation to partake of some form of vinegar to restore our body fluids to the correct pH. I believe this is the study mentioned in many ads in the back of magazines that mention the importance of a daily vinegar intake.

Anyway, I thought this would add some interest to the discussion.

milesawayfarm said...

This study about the pH of skin after using soap might help you better understand why alkali leave on products are troublesome (think of all the baking soda homemade deodorant issues), but soap, a wash off product, is not an issue. "RESULT: There were no differences between the pH of the skin these two groups prior to cleansing, immediately after cleansing or in the pH recovery rate for 6 h."

Carla P. Atallah said...

Thanks for this article! Someone once told me why not washing my face at all is better than using an inferior product, and this is probably a big part of the "why". I have a question. I'm working on making some lotion with oils, aloe and honey. Those all contain ph levels lower than typical skin. Are you telling me that it's fine to make my mix and not test it because they all have a lower acidity level than skin, or would it be preferable to raise the ph level to at least match my skin's ph? If the latter, can you suggest a quality ingredient that would raise the ph? Something that smells nicer than borax, perhaps... Thanks!

Susan Barclay-Nichols said...

Hi Carla. Can I recommend you read the other posts I've written on skin pH as some of your questions will be answered there. If you're making a lotion, it'll generally be around 5.5 to 6 pH, so don't worry about altering it. Please don't alter your pH without a good meter!