Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

Paula's Choice BHA 9 Treatment Versus Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel

Paula's Choice BHA 9 Treatment Versus Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel This acne treatment is formulated around Salicylic Acid to clear breakouts and refine the look of pores. This smoothing exfoliator is formulated around Glycoli

By Peptide Skincare & Beauty Editorial TeamPublished

Paula's Choice BHA 9 Treatment Versus Paula's Choice Skin Perfecting 25% AHA + 2% BHA Exfoliant Peel

This acne treatment is formulated around Salicylic Acid to clear breakouts and refine the look of pores.

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

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Propylene Glycol

PEG-75 Stearate

PEG-8

Water

Salicylic Acid

Glycerin

Avena Sativa Kernel Extract

Butylene Glycol

Boerhavia Diffusa Root Extract

Sea Whip Extract

Arginine

Polysorbate 20

Disodium EDTA

Propylene Glycol, PEG-75 Stearate, PEG-8, Water, Salicylic Acid, Glycerin, Avena Sativa Kernel Extract, Butylene Glycol, Boerhavia Diffusa Root Extract, Sea Whip Extract, Arginine, Polysorbate 20, Disodium EDTA

Aminomethyl Propanol

Glycolic Acid

Lactic Acid

Mandelic Acid

Isoamyl Laurate

Tartaric Acid

Propanediol

Malic Acid

Clitoria Ternatea Flower Extract

Sodium Hyaluronate

Glycyrrhetinic Acid

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

Reviews

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.

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. 03Also known as Avobenzone, this ingredient is an oil-soluble used to absorb the full spectrum of UVA rays (peak 357 nm).
  4. 04It's one of the most effective UVA filters available but has a major caveat of photostability: avobenzone is susceptible to photodegradation.
  5. 05This means it can lose efficacy when exposed to sunlight without the help of a stabilizing agent.
  6. 06Studies show antioxidants (like vitamin E or vitamin C) and some UV filters (like octocrylene and Tinosorb S) can meaningfully improve its stability in a formulation.
  7. 07The maximum allowable concentration according to regulation is 3% in the US + Canada, and 5% in the EU, Australia, China, Korea, and ASEAN countries.
  8. 08It has a well-support safety profile: a comprehensive 2025 review found minimal toxicity with no evidence of carcinogenicity.
  9. 09Overall, avobenzone is a safe and regulated ingredient used in sunscreen for over 40 years.
  10. 10Ethylhexyl Salicylate (also called Octisalate or Octyl Salicylate) is an oil-soluble organic UV filter that's been used in sunscreen since the 1950's.
  11. 11It absorbs UVB light in the 280-320 nm range with a peak absorbance around 306 nm.
  12. 12You'll often see it paired with other UV filters to boost overall SPF because octisalate is a fairly week filter on its own.
  13. 13The reason you'll see it so often is because it can help solubilize and stabilize the trickier filters like oxybenzone and avobenzone.
  14. 14Unlike these filters, octisalate has pretty good photostability and doesn't create skin-damaging free radicals when exposed to sunlight.
  15. 15The fatty-alcohol part of the molecule also gives it a light, emollient feel so it doubles as a nice texture enhancer.
  16. 16Usage levels vary around the world:
  17. 17Safety-wise, this ingredient has a pretty reassuring track record. The EU's Scientific Committee on Consumer Products (SCCP) found very low skin penetration in human skin tests and negative results for irritation, phototoxicity, and photoallergy.
  18. 18The real-world allergy risk is pretty low too; a 2012 European study of 1,031 people recorded only 2 reactions to it (a rate of 0.19%).
  19. 19You might have seen scary headlines about sunscreen getting into your blood.
  20. 20In 2019, the FDA found that several chemical filters can absorb through the skin and show up in the bloodstream at small but measurable levels.
Source · skinsort.com ⟶
02

Product index

Related product references

03

Comparison edit

Read side by side

Continue reading

Related articles