CHEMICAL PEELS 101: Acid Types

Updated: Apr 14



Which chemical acid peel is correct for your skin type? What is your skin type? And, how do chemical acid peels work?


Chemical peels are one of the most effective antiaging tools I use in my yearly skincare routine.

SHOP EVERYTHING MENTIONED





Naturally, different chemical peels vary in treatment, strength, and downtime. The overall concept of skin improvement via a chemical peel is to remove the outer layers of skin in order to reveal younger, tighter, more glowy skin.

Just like with microneedling, a chemical peel is a controlled wound that stimulates cell renewal and regenerates healthier layers of skin below the surface.


With so many factors, how do you decide which chemical peel to do?



My favorite acid peel is TCA. This is a strong acid and it will cause you to shed skin. This type of peel is shocking for most to experience and observe since your skin falls off in sheets for nearly a week. TCA is very effective at treating sun spots, wrinkles, pore size, and overall, it rejuvenates your complexion. Although TCA is my favorite acid peel, I use other acids all year long. So let's dig deep and look at all acids, what are their benefits, and how best to use them.


ACID PEEL VIDEOS

I have many peel video's up on YouTube chronicling my experiences and I have them grouped into an Acid Peel Playlist


TYPES OF ACIDS

FIRST: there are 3 categories of Hydroxy Acids:

  • Alpha-Hydroxy Acids

  • Beta-Hydroxy Acids

  • Poly-Hydroxy Acids (we will cover these in another post)

SECOND: Chemical peels are broken into 6 different types:

  1. Alpha Hydroxy Acids (AHA's)

  2. Beta Hydroxy Acids (BHA's)

  3. Trichloroacetic Acid (TCA)

  4. Blended Peels: Self-neutralizing

  5. Blended Peels: Requiring Neutralization

Chemical peels rely on acids to penetrate, coagulate proteins, denature, and overall clear outer skin cells to reveal more radiant-looking skin.


CHEMICAL PEEL BOOK

I have found this book to be very helpful when looking at peel options and how to best use them on myself.


HOW DOES THIS WORK?


The mechanism for skin releasing and falling off due to a chemical peel is called desquamation and it has to do with the above blue = called Desmosome.


There are two methods by which chemical peels remove the outer layers of skin:

  • Keratolysis is where an acid penetrates thru the stratum corneum, disrupting cellular connections (the "skin glue" or "skin cement") by breaking the bonds. Examples of these acids include:

  1. Glycolic

  2. Lactic

  3. Salicylic

  • Keratocoagulant is when a chemical agent actually coagulates the protein known as keratin causing it to denature, meaning change. Essentially, the acid is cooking the skin cells but not thermally (heat). Even though the burn from TCA feels thermal, it is actually a chemical change. An example I use when explaining this phenomenon is when you cook an egg white; the protein changes from clear to white. This egg illustration is actually caused by heat changing the protein, not a chemical. If you are familiar with making Ceviche from Latin America, this dish actually illustrates keratocoagulant best. In Ceviche acid is added to fish, it denatures the fish's protein, making it safe to eat without needing to add heat. Example:

  1. TCA


Different acids penetrate the stratum corneum (top layer of skin), disrupting the corneocyte adhesion by dissolving the desmosomal bonds, basically the glue keeping skin together. The deeper the acid can penetrate, breaking these desmosome bonds the more aggressive and higher risk the acid peel becomes.




The majority of chemical peels performed, especially many DIY at home will reside in the mid to upper epidermis. The depth at which any acid will go is based on the following:

  1. Chosen Acid

  2. Percentage Strength

  3. pH of Acid

  4. Time applied

  5. Application technique (applying pressure and rubbing vs light swab)

  6. Quantity of layers applied

  7. Skin preparation (Mechanical removal of top skin via microdermabrasion or dermaplaning; topicals such as lower strength acids and Retinoids)

  8. Skin type (Very oily and thick versus dry and thinned out skin)


ALPHA-HYDROXY ACID'S

Alpha-Hydroxy Acids are commonly referred to as AHA's.


DIFFERENT AHA MOLECULAR STRUCTURES


GLYCOLIC

  • Glycolic Acid – Made from SUGAR CANE, is probably the most popular AHA. It is fantastic for exfoliating and, since it also boasts antimicrobial properties, could help with acne breakouts too. (It won’t clear out the oil from deep within the pores in the same way as BHA, namely Salicylic). Glycolic has long been considered by many professionals to be the best performing acid. As the smallest hydroxyl acid molecule, glycolic acid can penetrate the skin, the deepest and the fastest.

  • Glycolic acid needs to be neutralized, this can be as simple as rinsing it off which will change the pH by diluting, or if it is a very high concentration then a basic solution to actually neutralize the acidic pH.

TAKE AWAY: Glycolic Acid is an AHA

Comes from Sugar

Smallest Molecule

Penetrates the fastest & deepest

Best for tightening skin & collagen stimulation

Must be NEUTRALIZED

LACTIC

  • Lactic Acid – derived from the lactose that is found in MILK. Lactic acid is known for its exfoliating and anti-aging benefits. Like all AHAs, lactic acid is great for general exfoliation and skin brightening. But because this is a larger molecule, the lactic acid does not penetrate as deeply into the skin’s surface as glycolic acid, causing it to be gentler and further, making this the AHA of choice for those with sensitive skin and darker pigmentation.

LACTIC PEEL VIDEO


TAKE AWAY: Lactic Acid is an AHA

Comes from Milk

Larger Molecule

Does not Penetrate as deeply

Hydrates upper levels of skin

Best for all skin types

Does not require Neutralization




MANDELIC

  • Mandelic Acid – made from ALMONDS. Mandelic acid is a highly effective, multitasking acid that helps address fine lines, firmness, acne, and discoloration. Because mandelic is a slightly larger molecule, it’s better for sensitive skin types and for skin types with higher concentrations of melanin because it doesn’t trigger post-inflammatory responses or pigmentation like we see from other AHAs. Due to Mandelic's antimicrobial properties, it’s effective against acne and clogged pores, similar to Salicylic.

  • A study compared a mandelic-salicylic acid combination peel with a glycolic peel, the combined mandelic-salicylic peel saw better overall results and had fewer side effects.

TAKE AWAY: Mandelic Acid is an AHA

Comes from Almonds

Larger Molecule

Does not Penetrate as deeply

Good for darker skin tones & sensitive skin

Mandelic acts similar to Salicilic

Does not require Neutralization

MANDELIC PEEL VIDEO



The mandalic peel is super gentle. I actually used this on Amazon Live and didn't even feel a tingle. You can watch the Mandelic Acid Peel Live HERE






MORE AHA's

There are additional AHAs; below are a few more, however, the others are not used alone in a chemical peel. Instead, they are combined into mixed acid peels with other AHA's or into popular daily skincare exfoliants, such as peel pads and glycolic toners. Further, there are additional mild AHAs that are combined into skincare products but I am not listing all of them.


  • Tartaric Acid – Generated from GRAPE extracts. Tartaric acid is not quite as common as glycolic and lactic but has a few distinct advantages. It is great for tackling acne breakouts and blemishes, while also minimizing the visible signs of sun damage.

  • But its primary benefit is its ability to regulate a formula's pH level, preventing skin irritation and stabilizing solutions, which is why it is paired often in Glycolic and Lactic acid skin serums. An example, of a balanced combination for brightening your skin, is this Dark Spot Corrector.


  • Citric Acid – as you can guess from its name, citric acid comes from CITRUS FRUITS. This AHA is fantastic at neutralizing the skin’s pH level, therefore preventing a whole host of skin issues from arising. Citric acid is also effective at evening out roughness and skin tone. An example is this Vitamin C Complex it has a mix of different citrus fruit acids plus citric acid.


  • Malic Acid – Derived from APPLES. Malic acid isn’t a very effective exfoliant when used on its own. However, it does a great job of increasing the effects of other AHAs when it has been combined with them. An example is this Glycolic Acid Serum that is enhanced with Malic acid.



BETA-HYDROXY ACID'S

Beta-Hydroxy Acids are commonly referred to as BHA'S.


SALICYLIC


30% Salicylic Peel At Home Natural Kaos

  • Salicyclic Acid - Comes from, WILLOW BARK, Wintergreen Oil & Sweet Birch. Salicylic acid is a type of phenolic acid with a chemical formula of C7H6O3. This acid is a BHA and 30% concentration is used for superficial peels. The acidic nature of salicylic acid makes it a good exfoliator with a powerful defense mechanism of your skin against bacteria (Propionibacterium acnes) that cannot survive in extremely acidic environments. It is also an effective treatment for warts caused by Human Papilloma Virus. It acts by breaking the small attachments joining your skin cells together (these are the desmosome bonds discussed earlier), thereby encouraging exfoliation (skin peeling) and unclogging of pores.

  • Salicylic acid has a lipid structure, meaning it can penetrate other lipids, like oil in your pores. This causes salicylic to seek out oily parts of the skin, such as pores, resulting in deep pore cleansing.

  • It should be noted, that while salicylic acid is proven effective against some acne, it does have its limitations. While BHA has been shown to be mildly antibacterial, it has not been shown to kill p. acnes bacteria, the most common bacteria that leads to acne. For this reason, salicylic acid is often paired with antibacterial ingredients or benzoyl peroxide for the best results. Salicylic acid can also be mildly drying to the skin, so it’s important to moisturize when using it.

  • Dermatologists recommend a salicylic acid formulation that contains 0.5% up to 2%(This added information is not for a SA peel but for insight on using SA in your daily protocol).

TAKE AWAY: Salicylic Acid is a BHA

Comes from Willow Bark

Lipid Structure

Can penetrate oily pores

Acne Control

Good for darker skin tones & sensitive skin

30% SA is a superficial peel concentration

Does not require Neutralization


20% Salicylic Acid

30% Salicylic Acid



TRICHLOROACETIC ACID (TCA)

Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an analog of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. Salts and esters of trichloroacetic acid are called trichloroacetates.

TCA 25% Natural Kaos
  • TCA is synthetically made from acetic acid and chlorine. TCA is the most potent acid peel I do at home and I've had great results using this acid. TCA is different from Hydroxy Acids as it does not break desmosome bonds to shed skin but instead chemically changes the nature of the protein Keratin, thru the process of Keratocoagulant, described above. TCA is also man-made whereas Hydroxy Acids are found naturally.

  • 20% TCA concentration is typically used for superficial peels. I previously obtained TCA acid from Amazon however, in the fall of 2020 Amazon stopped carrying TCA peels. I now find TCA concentrations on eBay.

TCA 30% + 5% Salicylic

TCA 25%

TCA 25% + 5% Salicylic

TCA 15%

TCA 10%

  • As previously explained, TCA peels the skin via the keratocoagulant process. This process is observed by the "frosting" of the skin.

  • As you apply TCA acid it can cause a whiteness in the skin. This cannot be wiped off, the discoloration or denaturing of the protein is observed and is called "frosting". After 30-60 minutes following application, the white will fade to a red sunburn.

  • Unlike glycolic acid, TCA does not need to be neutralized, however, once the depth of the peel is reached and illustrated by the white frost it can be stopped by diluting with water. This is not neutralizing the acid but rather diluting its strength which causes it to stop denaturing the keratin protein.

  • Lighter skin tones are best for TCA as opposed to darker skin that has more melanin and could result in hyperpigmentation spots.

  • TCA can be extremely painful as compared to other acid peels. 20% and 25% strengths can feel like a fire torch on your face.

  • TCA is ideal at:

  1. Removing freckles & Sunspots

  2. Evening out skin tone

  3. Improving texture

  4. Tightening Pores

  5. Reducing Fine Lines


TAKE AWAY: TCA is a man made acid

20% or lower is a superficial peel

Keratocoagulant

Self Neutralizes

Anti-aging peel

Lighter skin tones are best

Can be very painful

RECENT TCA VIDEO




BLENDED PEELS

My recent video on Youtube was actually a Blended Peel. It included 30% TCA + 5% Salicylic. This peel did not have any glycolic included therefore it did not need to be neutralized. I go into detail on this peel in a previous blog post.


TCA + SALICYLIC

The below excerpt is taken from this article

"Salicylic acid (ortho hydroxybenzoic acid) is a beta hydroxy acid agent. It is a lipophilic compound that produces desquamation of the stratum corneum via the removal of intercellular lipids [3] (see salicylic acid section). Given its keratolytic effects, it has become an increasingly popular superficial peeling agent. Salicylic acid peels induce injury via thinning or removal of the stratum corneum. In addition, salicylic acid potentially enhances the penetration of TCA. Trichloroacetic Acid (TCA) causes precipitation of proteins and coagulative necrosis of epidermal cells [4]. The extent of damage is indeed concentration-dependent. Concentrations range from 10 to 50%. Superficial TCA peeling is induced by concentrations of 10–30% whereas higher concentrations cause medium depth or deep peeling. The combination of salicylic acid followed by TCA 10–15% induces superficial wounding." Pearl E. Grimes


JESSNER'S = (Lactic, Salicyclic, & TCA in Equal Parts)

Blended peels can include many acids, Jessner's for instance is a 3-way blend of equal parts of Lactic, Salicylic, and Resorcinol.

This balance of acids is effective as the lactic hydrates, the salicylic breaks up rough skin cells and oil, and resorcinol has historically been used in the Jessner formula thanks to its natural antiseptic properties. Resorcinol is now being replaced by TCA as the third element due to health concerns.


Jessner's is typically 14% strength of each of these 3 components, but I have seen it in 10%, 20%, and 30%. I have personally used Jessner's 30% mix and I shared the experience in this video.

Jessner's does not require neutralizing as it does not include glycolic acid.


MIXED PEEL TAKE AWAY:

Looking at your own skin should lead you in the direction of what peel might serve you best. So much of this has to do with your skin color and what your Fitzpatrick Skin number is on the scale.

If you are skin type 1-3, your skin does not have as much melanin as skin types 4-6. This means when it comes to chemical peels lighter skin is more forgiving because it does not have the hyperpigmentation issues that darker skin types can present.


I am skin type 2 and my skin tone can tolerate high concentrations of single acids as well as mixed peels. I like a mix that clears pores, tightens, and fades sun damage. The recent TCA mixed with Salicylic was a very thorough peel which I felt comfortable with, however, the high concentrations can be adjusted to make this mixed peel better for darker skin tones.



If you have darker skin than me then instead of the 30% TCA mixed with 5% Salicylic a better option would be 20% Salicylic mixed with 10% Mandelic. This can be repeated 4 times every 2 weeks for a more controlled shedding that should prevent any hyperpigmentation.


Darker skin tones need to be most concerned about TCA concentrations greater than 10% and Glycolic concentrations greater than 30% as these 2 chemical peels can penetrate deep and can have side effects.

Darker skin tones should look for mixed peels that contain Salicylic, Lactic & Mandelic as these 3 acids are the best for darker complexions.


BLENDED PEELS: Requiring NEUTRALIZING

The only peels in this blog post that require neutralization are those that contain Glycolic Acid. Due to the small molecule size of Glycolic Acid, it can continue deep into the skin breaking the desmosomal bonds which connect skin cells. If the pH is not corrected Glycolic acid will continue to dismantle the skin.


Today, glycolic acid is in nearly every skincare product, every serum, every night cream, and skin toner; consequently, how can it be that it needs to be followed by neutralization?

During a recent Amazon Live when we were discussing all of these acids LIVE (this is still available to watch and make sure to FOLLOW+) the Ordinary Peeling Solution was brought up. This solution contains 30% AHA and 2% BHA, and the question was, does it need to be neutralized with an actual neutralizing solution?

I wondered the same thing...


I found an article that said, "At up to 10 percent concentration it [glycolic acid] can be neutralized and washed away with water. Skincare products containing more than 10 percent glycolic acid must be followed by a neutralizer. Professional chemical peels use concentrations of 20-70 percent glycolic acid. This requires a specially formulated neutralizer and should be done by someone with experience."


The Ordinary Peeling Solution has 30% AHA, but not necessarily 30% glycolic.


THE ORDINARY PEELING SOLUTION INGREDIENTS:

With 30% alpha hydroxy acids (glycolic/lactic/tartaric/citric), 2% beta hydroxy acid (salicylic acid), hyaluronic acid crosspolymer, vitamin b5, black carrot, and Tasmanian pepperberry.

Brands don't typically list their percentages of ingredients as it would give away their "special sauce" so I reason that in this solution there must be less than 10% glycolic acid as the directions simply indicate to rinse face with water after 10 minutes.



This peel, although mild does need to be rinsed off. I have a friend who spot-treated a blemish with this solution and did not wash it off. In the morning she noticed that it caused a good deal of desquamation to her skin where she had left it.


I have a SKINCARE ROUTINE on how to use this weekly here


Here is an example where again it becomes confusing on what is being marketed. Below this Glycolic Acid, Pads look like they have 35% Glycolic Acid in them.

Here is the back label and it looks like Glycolic must be a large percentage as it is listed second, however, I think this solution must have under 10% glycolic acid and the other 25% AHA is made up of the listed botanical extracts, and vitamin C. This is why you can use this daily, along with a good sunscreen.



MIXED PEEL WITH GLYCOLIC TAKE AWAY:

Glycolic Acid needs to be Neutralized with a pH balancing solution whenever it has a concentration over 10%. Bottles that contain this high of a percentage should state it or their instructions should inform you to use a pH neutralizer.

If a product says to wash with water it is under 10% and it should be removed after the appropriate time.

In the case of glycolic peel pads, these have low percentages of glycolic acid and will be diluted by other products you layer on, or even in the case you did not layer on anything further, they contain soothing ingredients that prevent deep penetration.


This is a peel pH Neutralizer and Prep Solution


HOW TO DECIDE?


I realize this is a lot of information to digest. My hope is that you come away from this post with these basic concepts:

  1. Your Skin Tone matters when it comes to chemical peels, so first identify what skin type you are on the Fitzpatrick Scale.

  2. There are a ton of AHAs options but the most common are:

  3. Glycolic requires neutralization of concentrations 10% and higher. It has the smallest molecular weight which is why it can penetrate deeply. Best for skin tightening and for lighter skin tones.

  4. Latic does not need to be neutralized. It is a much larger molecule and thus cannot penetrate deep making it ideal for darker skin tones.

  5. Salicylic is the most common BHA, it does not require neutralization, and it seeks to break up oily pores as it is lipophilic. Salicylic is ideal for those dealing with acne, however, it can be drying to your skin.

  6. There are 2 kinds of processes for breaking up skin cells:

  7. Keratolysis (AHAs & BHAs)

  8. Keratocoagulant (TCA)

  9. TCA breaks up skin cells by coagulating the protein, this is visible by the white frost that can be present based on concentration. This acid is severe and can cause scarring. Any TCA concentration over 30% is considered deep and one should seek professional help if planning this strength. TCA does not need to be neutralized however once you are happy with the extent of coagulation you can dilute its effect with cold water.

  10. Doing deep peels where your skin sheds in sheets is not a monthly protocol, this should only be done a couple of times per year, perhaps 2 times each fall-winter.


EXTRA INFO:)

Below is some extra information about Tranexamic Acid which I use in some of my nightly routines. TXA can be the solution for many who struggle with melasma and glycolic acid.

TRANEXAMIC ACID "TXA"



Unlike glycolic acid, lactic acid, and salicylic acid, tranexamic acid is not considered an exfoliating acid. "Its powerful anti-inflammatory action disrupts what is responsible for excessive melanin production and pigmentation," which appears in dark spots on the skin.

Also known as TXA, tranexamic acid is actually a bio-engineered amino acid. It has been used in medicine for many years to help reduce blood loss in patients during surgery. However, in terms of beauty, it has also been discovered that tranexamic acid is a tyrosinase inhibitor.


TYROSINASE?

"Tyrosinase is responsible for the first step in melanin production. It converts a protein building block (amino acid) called tyrosine to another compound called dopaquinone."


Basically, instead of acid causing melasma and sunspots to peel off, TXA actually stops the tyrosinase which is responsible for encouraging color in the skin from developing.


Have a great day xoxo

Kim



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