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Kiehl’s Powerful Strenght Line Reducing & Dark Circle Diminishing Vitamin C Eye Serum

Powerful Strenght Line Reducing & Dark Circle Diminishing Vitamin C Eye Serum

Vitamin C Eye Serum
Uploaded by: denisasimam on

Kiehl’s Powerful Strenght Line Reducing & Dark Circle Diminishing Vitamin C Eye Serum
Ingredients explained

What-it-does: moisturizer/humectant, solvent, viscosity controlling | Irritancy: 0 | Comedogenicity: 0
  • It's a helper ingredient that improves the freeze-thaw stability of products
  • It's also a solvent, humectant and to some extent a penetration enhancer
  • It has a bad reputation among natural cosmetics advocates but cosmetic scientists and toxicology experts do not agree (read more in the geeky details section)
Read all the geeky details about Propylene Glycol here >>

What-it-does: emollient | Irritancy: 0 | Comedogenicity: 1

Probably the most common silicone of all. It is a polymer (created from repeating subunits) molecule and has different molecular weight and thus different viscosity versions from water-light to thick liquid.

As for skincare, it makes the skin silky smooth, creates a subtle gloss and forms a protective barrier (aka occlusive). Also, works well to fill in fine lines and wrinkles and give skin a plump look (of course that is only temporary, but still, it's nice). There are also scar treatment gels out there using dimethicone as their base ingredient. It helps to soften scars and increase their elasticity. 

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As for hair care, it is a non-volatile silicone meaning that it stays on the hair rather than evaporates from it and smoothes the hair like no other thing. Depending on your hair type, it can be a bit difficult to wash out and might cause some build-up (btw, this is not true to all silicones, only the non-volatile types). 

Glycerin - superstar
Also-called: Glycerol | What-it-does: skin-identical ingredient, moisturizer/humectant | Irritancy: 0 | Comedogenicity: 0
  • A natural moisturizer that’s also in our skin
  • A super common, safe, effective and cheap molecule used for more than 50 years
  • Not only a simple moisturizer but knows much more: keeps the skin lipids between our skin cells in a healthy (liquid crystal) state, protects against irritation, helps to restore barrier
  • Effective from as low as 3% with even more benefits at higher concentrations up to 20-40% (around 10% is a good usability-effectiveness sweet spot)
  • High-glycerin moisturizers are awesome for treating severely dry skin
Read all the geeky details about Glycerin here >>

Ascorbic Acid - superstar
Also-called: Vitamin C, L-ascorbic acid | What-it-does: antioxidant, skin brightening, buffering
  • Works best between a concentration of 5-20%
  • Boosts the skin’s own collagen production
  • Fades pigmentation and brown spots
  • If used under sunscreen it boosts its UV protection
  • Extremely unstable and oxidizes very easily in presence of light or air
  • Stable in solutions with water only if pH is less than 3.5 or in waterless formulations
  • Vit E + C work in synergy and provide superb photoprotection
  • Ferulic acid doubles the photoprotection effect of Vit C+E and helps to stabilize Vit C
  • Potent Vit. C serums might cause a slight tingling on sensitive skin
Read all the geeky details about Ascorbic Acid here >>

A high-molecular-weight silicone elastomer (rubber-like elastic material) that is usually blended with a base silicone fluid (such as dimethicone or cyclopentasiloxane) to give the formula a silky smooth feel and to act as a thickening agent.

Also-called: Cetyl Dimethicone Copolyol | What-it-does: emulsifying, surfactant/cleansing

A silicone emulsifier that helps water and silicone oils to mix nicely together. 

What-it-does: emollient, solvent

A light-feeling, volatile (meaning it does not absorb into the skin but evaporates from it) silicone that gives skin a unique, silky and non-greasy feel. It has excellent spreading properties and leaves no oily residue or build-up. 

Also-called: Aqua;Water | What-it-does: solvent

Good old water, aka H2O. The most common skincare ingredient of all. You can usually find it right in the very first spot of the ingredient list, meaning it’s the biggest thing out of all the stuff that makes up the product. 

It’s mainly a solvent for ingredients that do not like to dissolve in oils but rather in water. 

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Once inside the skin, it hydrates, but not from the outside - putting pure water on the skin (hello long baths!) is drying. 

One more thing: the water used in cosmetics is purified and deionized (it means that almost all of the mineral ions inside it is removed). Like this, the products can stay more stable over time. 

What-it-does: buffering

We don't have description for this ingredient yet.

What-it-does: viscosity controlling

We don't have description for this ingredient yet.

A handy helper ingredient that comes in a white powder form and works as an anti-caking and oil-absorbing agent. It also gives products good spreadability, long lasting and velvet touch characteristics. It is popular both in skincare and makeup products.

A type of silicone elastomer (rubber-like material with both viscosity and elasticity) whose major function is forming a nice film on the skin.

It is also cosmetically very elegant with a non-tacky, non-oily and smooth skin feel. It also works as a stable delivery system of active materials, has sebum absorption and control properties and upon application, it transforms into a matte appearance with a powdery after feel.

Also-called: Titanium Dioxide/Ci 77891;Ci 77891 | What-it-does: colorant | Irritancy: 0 | Comedogenicity: 0

Ci 77891 is the color code of titanium dioxide. It's a white pigment with great color consistency and dispersibility.

Adenosine - goodie

Adenosine is an important little compound in our body that has a vital cell-signalling role. Research on smearing it on our face is also promising and shows so far a couple of things:

  • It can help with wound healing
  • It’s a good anti-inflammatory agent
  • It might even help with skin’s own collagen production and improve skin firmness and elasticity
  • It helps with barrier repair and protection
  • It might be even useful for the hair helping with hair thickness and hair growth
What-it-does: moisturizer/humectant

Hydrolyzed Hyaluronic Acid is a low molecular weight, chemically chopped up version of the naturally big molecule and current IT-moisturizer, Hyaluronic Acid (HA). The TL; DR version of HA is that it's a huge polymer (big molecule from repeated subunits) found in the skin that acts as a sponge helping the skin to retain water, making it plump and elastic. As HA is a polymer, the subunits can be repeated many times (as a high-molecular-weight version), or just a few times (as a low-molecular-weight version).

We wrote in detail at HA about how different molecular weight versions do different things both as a component of the skin and as a skincare ingredient, so click here and read about all the details. Hydrolyzed Hyaluronic Acid can also come in different molecular-weight versions with different properties:

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  • 100-300 kDa version: apart from moisturizing, this size might also help the skin to repair itself by increasing its self-defense. It is also claimed to boost the wound healing process and is especially helpful for sensitive skin types (acne, rosacea, inflammation-related skin diseases). 
  • 50k Da version: this is the size that is claimed to be able to absorb into the skin and plump up wrinkles, so it is used mainly as an "anti-aging ingredient" 
  • below 50k, around 10k Da version: there is a Japanese version trade named Hyalo-Oligo that has only a 10k molecular weight and is claimed to penetrate the skin very well, have a unique touch and give deep and long-lasting moisturization. Based on the Evonik-research and the natural role of LMW-HA in the body working as a pro-inflammatory signal molecule, this ultra-low molecular weight version is a controversial ingredient

If you wanna become a real HA-and-the-skin expert, you can read much more about the topic at hyaluronic acid (including penetration-questions, differences between high and low molecular weight versions and a bunch of references to scientific literature).

What-it-does: emulsifying, surfactant/cleansing | Irritancy: 1 | Comedogenicity: 2

A waxy solid material that helps oil and water to mix together, aka emulsifier. It is derived from the fatty alcohol called stearyl alcohol by ethoxylating it and thus making the molecule more water-soluble.

The end result is a mostly water-loving emulsifier, also called solubilizer that can help to dissolve small amounts of oil-loving ingredients into water-based products. Or it can be combined with more oil-loving emulsifiers (such as its sister, Steareth-2) to create stable emulsions. 

We don't have description for this ingredient yet.

We don't have description for this ingredient yet.

What-it-does: chelating, buffering

A little helper ingredient that is used to adjust the pH of the product. It also helps to keep products stay nice longer by neutralizing the metal ions in the formula (they usually come from water). 

What-it-does: preservative

It's one of those things that help your cosmetics not to go wrong too soon, aka a preservative. It’s not a strong one and doesn’t really work against bacteria, but more against mold and yeast. To do that it has to break down to its active form, sorbic acid. For that to happen, there has to be water in the product and the right pH value (pH 3-4). 

But even if everything is right, it’s not enough on its own. If you see potassium sorbate you should see some other preservative next to it too.

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BTW, it’s also a food preservative and even has an E number, E202.

Also-called: Part of Matrixyl 3000, Pal-GHK, Formerly also Palmitoyl Oligopeptide | What-it-does: cell-communicating ingredient

A really famous peptide that is part of Matrixyl 3000, the most sold peptide complex in the word. Before we go and find out what the big deal with Matrixyl 3000 is, let's just focus on Palmitoyl Tripeptide-1 itself for a bit.

It's a small three amino acid (they are the building blocks of all proteins) peptide with the amino sequence of glycine-histidine-lysine, or GHK. GHK is attached to palmitic acid (a fatty acid) to increase oil solubility and skin penetration. 

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The GHK part is the important one as it's a type I collagen fragment. When collagen naturally breaks down in the skin, the resulting peptide fragments signal to the skin that it should get to work and create some nice, new collagen. Adding in collagen fragment peptides, like GHK, might trick the skin into thinking that collagen has broken down and it's time to create some more.

Therefore, Palmitoyl Tripeptide-1 is believed to be able to stimulate collagen production in the skin, and more collagen means fewer wrinkles and younger looking skin. 

In Matrixyl 3000, Palmitoyl Tripeptide-1 is coupled with Palmitoyl Tetrapeptide-7  and the duo works in synergy to reduce wrinkles and give younger looking skin. According to the manufacturer's in-vivo (made on real people) test, applying 3% Matrixyl 3000 twice a day for 2 months resulted in all of the following things:

  • 39.4% reduction in surface occupied by deep wrinkles
  • 32.9% reduction in main wrinkle density
  • 19.9% reduction in main wrinkle average depth
  • 16% improvement in roughness
  • 16.2% in lifting effect
  • 5.5% improvement in elasticity
  • 15.5% improvement in skin tone

Manufacturer results, of course, always have to be taken with a pinch of salt, but if you like peptides, the Matryxil 3000 duo is one of the best-proven and most well-known ones and it's something that is worth trying.

We don't have description for this ingredient yet.

Also-called: Tinogard TT;Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate | What-it-does: antioxidant, preservative

Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate is an antioxidant molecule used in small amounts (less than 0.8%) to help products stay nice longer. More specifically, it is great at preventing discoloration or other types of oxidative degradation. It is a trendy alternative to often bad-mouthed synthetic antioxidant and stabilizer, BHT

Also-called: Part of Matrixyl 3000, Pal-GQPR, Previously Palmitoyl Tetrapeptide-3 | What-it-does: cell-communicating ingredient

A four amino acid peptide with the amino sequence of glycine-glutamine-proline-arginine. It is attached to palmitic acid (a fatty acid)  to increase oil solubility and skin penetration. 

It works by reducing the production of the signal moleculeinteleukin-6 (IL-6) which promotes inflammation in the skin and less inflammation means slower degradation of important things (like collagen) that results in younger looking skin for a longer time. 

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It works in synergy with its pal, Palmitoyl Tripeptide-1 in the famous Matrixyl 3000 complex. You can read some more about the famous duo here.

What-it-does: buffering

Citric acid comes from citrus fruits and is an AHA. If these magic three letters don’t tell you anything, click here and read our detailed description on glycolic acid, the most famous AHA. 

So citric acid is an exfoliant, that can - just like other AHAs - gently lift off the dead skin cells of your skin and make it more smooth and fresh. 

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There is also some research showing that citric acid with regular use (think three months and 20% concentration) can help sun-damaged skin, increase skin thickness and some nice hydrating things called glycosaminoglycans in the skin. 

But according to a comparative study done in 1995, citric acid has less skin improving magic properties than glycolic or lactic acid. Probably that’s why citric acid is usually not used as an exfoliant but more as a helper ingredient in small amounts to adjust the pH of a formulation. 

Also-called: Vitamin H

Also called vitamin H, biotin is the main component of many enzymes in our body. A nice ingredient to take as a supplement for stronger nails and hair. When you do not take it as a supplement its effects are a bit more questionable but according to manufacturer info it can smooth the skin and strengthen the hair.

You may also want to take a look at...

what‑it‑does moisturizer/humectant | solvent | viscosity controlling
irritancy, com. 0, 0
A common glycol that improves the freeze-thaw stability of products. It's also a solvent, humectant and to some extent a penetration enhancer. [more]
what‑it‑does emollient
irritancy, com. 0, 1
A very common silicone that gives both skin and hair a silky smooth feel. It also forms a protective barrier on the skin and fills in fine lines. Also used for scar treatment. [more]
what‑it‑does skin-identical ingredient | moisturizer/humectant
irritancy, com. 0, 0
A real oldie but a goodie. Great natural moisturizer and skin-identical ingredient that plays an important role in skin hydration and general skin health. [more]
what‑it‑does antioxidant | skin brightening | buffering
Pure Vitamin C. A skincare superstar that is clinically proven to boost collagen production (in 5-20% concentration), fade hyperpigmentation and boost UV protection under sunscreen. Also, it's extremely unstable and hard to formulate. [more]
what‑it‑does viscosity controlling
A high-molecular-weight silicone elastomer (rubber-like elastic material) that is usually blended with a base silicone fluid (such as dimethicone or cyclopentasiloxane) to give the formula a silky smooth feel and to act as a thickening agent. [more]
what‑it‑does emulsifying | surfactant/cleansing
A silicone emulsifier that helps water and silicone oils to mix nicely together. 
what‑it‑does emollient | solvent
A light-feeling, volatile silicone that gives skin a unique, silky and non-greasy feel. It has excellent spreading properties and leaves no oily residue or build-up. 
what‑it‑does solvent
Normal (well kind of - it's purified and deionized) water. Usually the main solvent in cosmetic products. [more]
what‑it‑does buffering
what‑it‑does viscosity controlling
what‑it‑does viscosity controlling
A handy helper ingredient that comes in a white powder form and works as an anti-caking and oil-absorbing agent. It also gives products good spreadability, long lasting and velvet touch characteristics.
A type of silicone elastomer (rubber-like material with both viscosity and elasticity) whose major function is forming a nice film on the skin. [more]
what‑it‑does colorant
irritancy, com. 0, 0
Titanium dioxide as a colorant. It's a white pigment with great color consistency and dispersibility.
what‑it‑does cell-communicating ingredient
An important compound in our body that has a vital cell-signalling role. It is wound healing, anti-inflammatory and can help with barrier repair. [more]
what‑it‑does moisturizer/humectant
Hydrolyzed Hyaluronic Acid is a low molecular weight, chemically chopped up version of the naturally big molecule and current IT-moisturizer, Hyaluronic Acid (HA). The TL; [more]
what‑it‑does emulsifying | surfactant/cleansing
irritancy, com. 1, 2
A waxy solid material that helps oil and water to mix together, aka emulsifier. It is derived from the fatty alcohol called stearyl alcohol by ethoxylating it and thus making the molecule more water-soluble.The end result is a mostly water-loving emulsifier, also called solubilizer that can help to dissolve small amounts of oil-loving ingredients into water-based  [more]
what‑it‑does antimicrobial/antibacterial | preservative
what‑it‑does chelating | buffering
A helper ingredient that is used to adjust the pH of the product. Also helps to keep products stay nice longer by neutralizing the metal ions in the formula. 
what‑it‑does preservative
A not so strong preservative that doesn’t really work against bacteria, but more against mold and yeast. [more]
what‑it‑does cell-communicating ingredient
A three amino acid peptide that is part of famous peptide duo, Matrixyl 3000. It's a type I collagen fragment that might be able to trick the skin to think that collagen broke down and it's time to create some new one. [more]
what‑it‑does antioxidant | preservative
Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate is an antioxidant molecule used in small amounts (less than 0.8%) to help products stay nice longer. More specifically, it is great at preventing discoloration or other types of oxidative degradation. [more]
what‑it‑does cell-communicating ingredient
The pal of Palmitoyl Tripeptide-1 in Matrixyl 3000. A four amino acid peptide that works by reducing the production of the signal molecule, inteleukin-6 (IL-6) that promotes inflammation in the skin. [more]
what‑it‑does buffering
An AHA that comes from citrus fruits. It is usually used as a helper ingredient to adjust the pH of the formula. [more]
Vitamin H is a great supplement for stronger nails and hair. As a skincare ingredient, it's a bit more questionable, but it might smooth the skin and strengthen the hair. [more]