Peptide Skincare & BeautySkin science and ingredient guides

Skin science article

The Ordinary Caffeine Solution 5% + EGCG Versus Paula's Choice C15 Super Booster

The Ordinary Caffeine Solution 5% + EGCG Versus Paula's Choice C15 Super Booster This calming eye moisturizer is formulated around Caffeine and Epigallocatechin Gallatyl Glucoside to calm redness and soften the look of wrinkles. This brightening serum is formu

The Ordinary Caffeine Solution 5% + EGCG Versus Paula's Choice C15 Super Booster

This calming eye moisturizer is formulated around Caffeine and Epigallocatechin Gallatyl Glucoside to calm redness and soften the look of wrinkles.

This brightening serum is formulated around Ascorbic Acid and Ferulic Acid to brighten dull-looking skin and soften the look of wrinkles.

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Caffeine

Maltodextrin

Glycerin

Propanediol

Epigallocatechin Gallatyl Glucoside

Gallyl Glucoside

Hyaluronic Acid

Oxidized Glutathione

Melanin

Glycine Soja Seed Extract

Pentylene Glycol

Hydroxyethylcellulose

Polyacrylate Crosspolymer-6

Xanthan Gum

Lactic Acid

Dehydroacetic Acid

Trisodium Ethylenediamine Disuccinate

Propyl Gallate

Dimethyl Isosorbide

Benzyl Alcohol

1,2-Hexanediol

Ethylhexylglycerin

Phenoxyethanol

Caprylyl Glycol

Water, Caffeine, Maltodextrin, Glycerin, Propanediol, Epigallocatechin Gallatyl Glucoside, Gallyl Glucoside, Hyaluronic Acid, Oxidized Glutathione, Melanin, Glycine Soja Seed Extract, Pentylene Glycol, Hydroxyethylcellulose, Polyacrylate Crosspolymer-6, Xanthan Gum, Lactic Acid, Dehydroacetic Acid, Trisodium Ethylenediamine Disuccinate, Propyl Gallate, Dimethyl Isosorbide, Benzyl Alcohol, 1,2-Hexanediol, Ethylhexylglycerin, Phenoxyethanol, Caprylyl Glycol

Ascorbic Acid

Dipropylene Glycol

Ethoxydiglycol

Sodium Hydroxide

PPG-26-Buteth-26

PEG-40 Hydrogenated Castor Oil

Bisabolol

Ferulic Acid

Sodium Phytate

Decylene Glycol

Tocopherol

Sphingomonas Ferment Extract

Water, Ascorbic Acid, Dipropylene Glycol, Propanediol, Glycerin, Ethoxydiglycol, Sodium Hydroxide, PPG-26-Buteth-26, PEG-40 Hydrogenated Castor Oil, Bisabolol, Ferulic Acid, Sodium Phytate, Decylene Glycol, Tocopherol, 1,2-Hexanediol, Sphingomonas Ferment Extract, 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.

1,2-Hexanediol is a synthetic liquid and another multi-functional powerhouse.

It is a:

Humectant, drawing moisture into the skin

Emollient, helping to soften skin

Solvent, dispersing and stabilizing formulas

Preservative booster, enhancing the antimicrobial activity of other preservatives

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.

Phenoxyethanol is one of the most widely used preservatives in skincare (and for good reason!).

It 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.

On 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.

Another perk of this ingredient is that it stays functional across a wide pH range (3-10).

You'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.

Typical use concentrations range from 0.3-1% depending on the formula, and this ingredient is capped at 1% int the EU.

Safety-wise, the fear mongering does not hold up to the evidence. The EU's Scientific Committee on Consumer Safety and FDA consider it safe as a preservative at up to 1%, including for children of all ages.

Adverse systemic effects only showed up in animal studies at exposures roughly 200x higher than what people get from cosmetics. And despite its very widespread use, this ingredient is a rare sensitizer and allergic reactions are uncommon.

Propanediol is an all-star ingredient. It softens, hydrates, and smooths the skin.

It’s often used to:

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

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.

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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. 03Ascorbyl Glucoside (AA-2G) is one of the most stable vitamin C derivatives out there.
  4. 04It's made by attaching a glucose molecule to ascorbic acid; this glucose "cap" shields the vitamin C from air, light, heat, and metal ions that normally cause pure ascorbic acid to oxidize.
  5. 05Once on your skin, the enzyme alpha-glucosidase snips off the glucose and gradually releases active ascorbic acid right where it's needed. Basically, it behaves like a slow-release pro-vitamin C with less of a stinging that high-strength ascorbic ac…
  6. 06The research supports the classic vitamin C benefits as well. In lab and human studies, AA-2G slowed down the skin's production of melanin (the pigment behind dark spots) and helped shield skin cells against sun damage better than ascorbyl phosphate.
  7. 07These studies also showed AA-2G released vitamin C over a longer period.
  8. 08A frequently cited manufacturer trial found that a 2% AA-2G face cream significantly improved wrinkle depth and skin roughness after 45 days.
  9. 09And in 2009, a clinical trial showed it meaningfully lightened dark patches on the gums compared to a placebo.
  10. 10There's also collagen-synthesis support (since vitamin C is a required cofactor for that) and an antioxidant effect too.
  11. 11Typical usage is usually between 0.5-5% and most studies/products land around 2%.
  12. 12AA-2G performs best when formulated at a mildly acidic pH (~5-7) which is much gentler than the pH that pure vitamin C demands (~2.5-3.5).
  13. 13Just one thing worth knowing: the in-skin conversation rate is only about 55-60% by weight. So a 5% AA-2G product delivers roughly 2.75-3% of actual active vitamin C. On top of that, skin absorption is relatively low because the ingredient is water-…
  14. 14Citric Acid is an alpha hydroxy acid (AHA) naturally found in citrus fruits like oranges, lemons, and limes.
  15. 15Like other AHAs, citric acid can exfoliate skin by breaking down the bonds that hold dead skin cells together. This helps reveal smoother and brighter skin underneath.
  16. 16However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.
  17. 17Due to this, citric acid is usually included in small amounts as a pH adjuster. This helps keep products slightly more acidic and compatible with skin's natural pH.
  18. 18In skincare formulas, citric acid can:
  19. 19While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.
  20. 20Most citric acid used in skincare today is made by fermenting sugars (usually from molasses). This synthetic version is identical to the natural citrus form but easier to stabilize and use in formulations.
Source · skinsort.com
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Product index

Related product references

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Comparison edit

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