Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel Versus boscia Berry Blend Smoothing Facial with 28% Acid Complex

Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel Versus boscia Berry Blend Smoothing Facial with 28% Acid Complex This smoothing exfoliator is formulated around Glycolic Acid and Lactic Acid to refine skin texture and brighten dull-looking skin.

Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel Versus boscia Berry Blend Smoothing Facial with 28% Acid Complex

This smoothing exfoliator is formulated around Glycolic Acid and Lactic Acid to refine skin texture and brighten dull-looking skin.

This wash off mask is formulated around Salicylic Acid to clear breakouts and unclog pores.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Aminomethyl Propanol

Glycolic Acid

Lactic Acid

Mandelic Acid

Isoamyl Laurate

Tartaric Acid

Propanediol

Salicylic Acid

Malic Acid

Butylene Glycol

Clitoria Ternatea Flower Extract

Sodium Hyaluronate

Glycyrrhetinic Acid

Glycerin

Tocopherol

Bisabolol

Allantoin

Hydroxyethylcellulose

Hydrogenated Lecithin

Xanthan Gum

Polyglyceryl-4 Laurate

Polyacrylate Crosspolymer-6

Titanium Dioxide

Mica

Phenoxyethanol

Water, Aminomethyl Propanol, Glycolic Acid, Lactic Acid, Mandelic Acid, Isoamyl Laurate, Tartaric Acid, Propanediol, Salicylic Acid, Malic Acid, Butylene Glycol, Clitoria Ternatea Flower Extract, Sodium Hyaluronate, Glycyrrhetinic Acid, Glycerin, Tocopherol, Bisabolol, Allantoin, Hydroxyethylcellulose, Hydrogenated Lecithin, Xanthan Gum, Polyglyceryl-4 Laurate, Polyacrylate Crosspolymer-6, Titanium Dioxide, Mica, Phenoxyethanol

Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer

Sodium Hydroxide

Pyrus Malus Fruit Extract

Fragaria Ananassa Fruit Extract

Vaccinium Angustifolium Fruit Extract

Ribes Nigrum Fruit

Lactobacillus/Punica Granatum Fruit Ferment Extract

Citric Acid

Salix Nigra Bark Extract

Simmondsia Chinensis Seed Extract

Epilobium Angustifolium Flower/Leaf/Stem Extract

Aloe Barbadensis Flower Extract

Corallina Officinalis Extract

Ocimum Sanctum Leaf Extract

Curcuma Longa Root Extract

Solanum Melongena Fruit Extract

Coccinia Indica Fruit Extract

Melia Azadirachta Flower Extract

Melia Azadirachta Leaf Extract

Leuconostoc/Radish Root Ferment Filtrate

Theobroma Cacao Shell Powder

1,2-Hexanediol

Caprylyl Glycol

Buteth-3

Tributyl Citrate

Sodium Polyacrylate

Sodium Benzotriazolyl Butylphenol Sulfonate

Water, Glycolic Acid, Butylene Glycol, Glycerin, Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Sodium Hydroxide, Hydroxyethylcellulose, Malic Acid, Pyrus Malus Fruit Extract, Fragaria Ananassa Fruit Extract, Vaccinium Angustifolium Fruit Extract, Ribes Nigrum Fruit, Lactobacillus/Punica Granatum Fruit Ferment Extract, Salicylic Acid, Lactic Acid, Citric Acid, Salix Nigra Bark Extract, Simmondsia Chinensis Seed Extract, Epilobium Angustifolium Flower/Leaf/Stem Extract, Aloe Barbadensis Flower Extract, Corallina Officinalis Extract, Ocimum Sanctum Leaf Extract, Curcuma Longa Root Extract, Solanum Melongena Fruit Extract, Coccinia Indica Fruit Extract, Melia Azadirachta Flower Extract, Melia Azadirachta Leaf Extract, Leuconostoc/Radish Root Ferment Filtrate, Theobroma Cacao Shell Powder, 1,2-Hexanediol, Caprylyl Glycol, Buteth-3, Tributyl Citrate, Sodium Polyacrylate, Sodium Benzotriazolyl Butylphenol Sulfonate

Reviews

Be the first to review

Alternatives

Ingredients Explained

These ingredients are found in both products.

Ingredients higher up in an ingredient list are typically present in a larger amount.

Butylene Glycol (or BG) is used within cosmetic products for a few different reasons:

Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.

Though this ingredient works well with most skin types, some people with sensitive skin may experience a reaction such as allergic rashes, closed comedones, or itchiness.

Glycerin (or glycerol) is a compound naturally found in your skin. It's a powerhouse humectant that pulls water into the stratum corneum.

Topically, glycerin does several things at once:

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

Glycolic Acid is arguably the most famous alpha hydroxy acid (AHA) with tons of research backing its benefits.

It is found naturally in sugar cane but the form used in skincare is usually synthetic for purity and stability.

Glycolic acid removes the top layer of dead skin cells to allow newer and fresher ones to emerge.

AHAs work by breaking down the structural “glue” that holds old skin cells in place. When that buildup is gone, your skin can renew itself more efficiently.

Research also shows glycolic acid stimulates collagen production, helping to firm and thicken the skin over time. This is one of its biggest advantages over other AHAs.

Overall, glycolic acid helps with:

Fun fact: Glycolic acid boosts skin hydration by helping it produce molecules that increase hyaluronic acid naturally.

To work best, glycolic acid products should have a pH between 3-4 (that’s where exfoliation is most effective but still gentle on skin).

The pH and concentration of a product are key to its effectiveness:

It is normal to feel a slight stinging sensation when using glycolic acid. This usually fades as your skin adjusts.

Because glycolic acid has the smallest molecular size in the AHA family, it can penetrate deeper, which enhances its effectiveness but also makes it more likely to irritate sensitive skin.

If your skin is very sensitive or prone to rosacea, glycolic acid may be too strong; in that case, try milder options like lactic acid or a PHA instead.

Recent studies suggest glycolic acid might even help protect against UV damage. But don’t skip sunscreen! Freshly exfoliated skin is more sensitive to the sun.

Glycolic acid is a skincare superstar. It smooths, brightens, hydrates, and firms the skin. Unless you’re highly sensitive, it’s well worth adding to your routine.

Read more about some other popular AHA's here:

Hydroxyethylcellulose is used to improve the texture of products. It is created from a chemical reaction involving ethylene oxide and alkali-cellulose. Cellulose is a sugar found in plant cell walls and help give plants structure.

This ingredient helps stabilize products by preventing ingredients from separating. It can also help thicken the texture of a product.

This ingredient can also be found in pill medicines to help our bodies digest other ingredients.

Lactic Acid is another well-loved alpha hydroxy acid (AHA). It is gentler than glycolic acid but still highly effective.

Its main role is to exfoliate the surface of the skin by loosening the “glue” that holds dead skin cells together. Shedding those old cells leads to smoother, softer, and more even-toned skin.

Because lactic acid molecules are larger than glycolic acid, they don’t penetrate as deeply. This means they’re less likely to sting or irritate, making it a great choice for beginners or those with sensitive skin.

Like glycolic acid, it can:

Lactic acid also acts as a humectant (like hyaluronic acid). It can draw water into the skin to improve hydration and also plays a role in the skin's natural moisturizing factor (NMF) in the form of sodium lactate.

Studies show it can boost ceramide production to strengthen the skin barrier and even help balance the skin’s microbiome.

To get results, choose products with a pH between 3-4.

Lower strengths (5-12%) focus on surface exfoliation; higher strengths (12% and up) can reach deeper in the dermis (deeper, supportive layer) to improve skin texture and firmness over time.

Though it was originally derived from milk, most modern lactic acid used in skincare is vegan. It is made through non-dairy fermentation to create a bio-identical and stable form suitable for all formulations.

When lactic acid shows up near the end of an ingredient list, it usually means the brand added just a tiny amount to adjust the product’s pH.

Legend has it that Cleopatra used to bathe in sour milk to help reduce wrinkles.

Lactic acid is truly a gentle multitasker: it exfoliates, hydrates, strengthens, and brightens. It's a great ingredient for giving your skin a smooth, glowing, and healthy look without the harshness of stronger acids.

Malic Acid is an acid with both AHA and BHA properties, but is considered an AHA because its AHA properties are stronger.

It can be naturally found in unripe fruit and especially apples (its name from the latin word "malum", meaning apple!).

Like other AHAs, malic acid gently removes the top layer of dead skin cells to reveal smoother, brighter skin underneath.

Though it’s considered milder and less potent than glycolic or lactic acid, it can help improve:

Due to its larger molecular structure, it penetrates the skin more slowly and is often used in combination with other AHAs to enhance their overall effectiveness.

Malic acid often plays a role in balancing a product’s pH and is usually included in small amounts (around 1-2%) as a supporting exfoliant.

As with all exfoliating acids, you should wear sunscreen daily when using malic acid to protect your newly resurfaced skin.

Fun fact: Malic acid is the compound responsible for the tart flavor of apples and other sour fruits.

While research on malic acid is limited compared to glycolic or lactic acid, it’s still a safe and mild exfoliant.

Salicylic Acid (also known as beta hydroxy acid or BHA) is a well-known ingredient for treating skin that struggles with acne and clogged pores. It exfoliates both the skin's surface and deep within the pores to help clear out buildup, control oil, and reduce inflammation.

Unlike AHAs (alpha hydroxy acids), salicylic acid is oil-soluble. This allows it to penetrate into pores which makes it especially effective for treating blackheads and preventing future breakouts.

Salicylic acid is also known for its soothing properties. It has a similar structure to aspirin and can calm inflamed or irritated skin, making it a good option for acne-prone skin that is also sensitive.

Concentrations of 0.5-2% are recognized by the U.S. FDA as an over-the-counter topical acne product.

It can cause irritation and/or dryness if one's skin already has a compromised moisture barrier, so it's best to focus on repairing that before introducing this ingredient into your routine.

While salicylic acid does not increase sun sensitivity, it’s still important to wear sunscreen daily to protect your skin.

If you are looking for the ingredient called BHA or Butylated Hydroxyanisole, click here.

Water. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.

So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.

You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!

Similar Comparisons

The reference edit

Ingredients, questions
& further reading.

Connected source records selected through this article’s public topic index.

01

Formula cabinet

Ingredients & structured notes

Ingredient index

Ingredients Explained

  1. 01These ingredients are found in both products.
  2. 02Ingredients higher up in an ingredient list are typically present in a larger amount.
  3. 03Glycerin (or glycerol) is a compound naturally found in your skin. It's a powerhouse humectant that pulls water into the stratum corneum.
  4. 04Topically, glycerin does several things at once:
  5. 05Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.
  6. 06Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.
  7. 07This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.
  8. 08Just know very high concentrations (>40%) can feel tacky in low humidity.
  9. 09Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.
  10. 10PEG-40 Hydrogenated Castor Oil is an emulsifier derived from castor oil.
  11. 11As an emulsifying agent, it helps other ingredients like fragrances and fat-soluble vitamins dissolve cohesively.
  12. 12Due to its large molecule size, it doesn't penetrate beyond the skin's surface.
  13. 13This ingredient has a solid regulatory track record; the CIR Expert Panel first concluded it was safe for use in cosmetics at concentrations up to 100% in 1997. A 2012 reassessment reaffirmed that finding. Safety studies have also found no irritatio…
  14. 14A 2019 study did find this ingredient to grow Malassezia, so this ingredient may not be fungal acne safe.
  15. 15Phenoxyethanol is one of the most widely used preservatives in skincare (and for good reason!).
  16. 16It has a large spectrum of antimicrobial activity and especially effective bacteria, yeast, and mold while only having a weak effect on your skin's natural microbiome.
  17. 17On a cellular level, it disrupts the cell membranes of microbes by poking holes that make the cell leak. This shuts down the chemical reactions the microbe needs to make energy so it can no longer survive.
  18. 18Another perk of this ingredient is that it stays functional across a wide pH range (3-10).
  19. 19You'll often see it paired with boosters like Ethylhexylglycerin; one study showed that a 1:9 ratio of Ethylhexylglycerin to Phenoxyethanol damages bacterial membranes as effectively as doubling the Phenoxyethanol concentration on its own.
  20. 20Typical use concentrations range from 0.3-1% depending on the formula, and this ingredient is capped at 1% int the EU.
Source · skinsort.com
02

Product index

Related product references

03

Comparison edit

Read side by side