AHC Beauty The Real Eye Cream for Face Versus Sulwhasoo Essential Refining Eye Cream

It plays several roles in a formula:

Typical use levels for this ingredient sit around 1-10% and the Cosmetic Ingredient Review Expert Panel has affirmed safety at concentrations up to 25% in leave-on products.

Multiple assessments have found it to be non-irritating and non-sensitizing to most people.

However, there have been some cases of allergic contact dermatitis in patients with chronically compromised skin barriers.

Cetearyl alcohol has a comedogenic rating of 2 and irritancy rating of 1. Both of these numbers come from the 1989 study that used rabbit ears; a "2" means mildly comedogenic and a "1" means low irritancy.

Here's the catch: rabbit skin is more sensitive than human skin and throws a lot of false positives. A 1996 reappraisal found that ingredients rated 1-2 in the rabbit ear tests are generally safe for humans.

Remember comedogenic ratings are unable to assess the entire formula of a product or how it will react on your skin. Just be sure to patch test if you are unsure about certain ingredients.

This ingredient is not fungal acne safe. Cetearyl alcohol is a fatty alcohol with chain lengths that fall within the range that Malassezia can metabolize.

A 2019 study has also observed Malassezia growth in the presence of this ingredient, confirming it to be not-fungal acne safe.

The safety profile of this ingredient is reassuring; the US CIR Expert Panel concluded D5 is safe as used in cosmetics and Health Canada concluded that D5 is not harmful to human health or the environment as currently used in cosmetics

There's a study that people mention about D5 in a rat study showing tumors. This study is related to long-term inhalation of high D5 levels.

Regulatory bodies have judged this study to be not applicable in topical skincare since skin absorption of D5 is very low and we're not really inhaling huge amounts of D5.

The only restriction for this ingredient is environmental. The European Chemicals Agency (ECHA) restricted D5 in wash-off cosmetics at or above 0.1% due to their persistence in water.

Dimethicone comes in different viscosities:

Depending on the viscosity, dimethicone has different properties.

Ingredients lists don't always show which type is used, so we recommend reaching out to the brand if you have questions about the viscosity.

This ingredient is unlikely to cause irritation because it does not get absorbed into skin. However, people with silicone allergies should be careful about using this ingredient.

Note: Dimethicone may contribute to pilling. This is because it is not oil or water soluble, so pilling may occur when layered with products. When mixed with heavy oils in a formula, the outcome is also quite greasy.

On top of that, this ingredient can counteract the effects of hard water by binding to the minerals in it.

One thing worth knowing is that Disodium EDTA has been shown to be a mild penetration enhancer. It can help other ingredients absorb into skin more effectively which can be a double-edged sword (great for actives, but can also make the active too strong if you have sensitive skin).

Clinical patch testing showed no significant skin irritation at typical use concentrations and minimal dermal absorption.

You'll most likely see this ingredient near the end of an ingredient list. It's typically found in concentrations less than 1%.

Industry-reported use ranges from 8% in rinse-off products and 2% in leave-on formulations.

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.

This ingredient is an emollient, emulsifier, and penetration enhancer. As an emollient, it helps soften and hydrate skin by trapping moisture within. As an emulsifier, it prevents oil and water ingredients from separating.

Hydrogenated Lecithin can form tiny spherical structures made of phospholipid bilayers called liposomes. These liposomes are able to capture compounds inside their structure and deliver them through the skin barrier.

Because phospholipids are a natural component of our cell membranes, this ingredient is inherently compatible with skin.

A 2021 study found lecithin-based surfactants were less harsh and more tolerable comared to Sodium Lauryl Sulfate (SLS).

Interestingly, topically applied Palmitic Acid can be elongated into longer chain fatty acids and ceramides. A 2019 study found low levels of Palmitic Acid lead to slower development of cells, suggesting it plays a role in keeping your skin's renewal process on track.

The CIR (Cosmetic Ingredient Review) panel determined it safe as used in cosmetics at concentrations up to 13%. It is non-irritating and non-sensitizing in clinical studies.

The culprit behind fungal acne, the Malassezia yeast, feeds on fatty acids with carbon chain lengths between C11-C24. Palmitic Acid, at C16, falls right into that sweet spot.

In vitro studies have shown that Palmitic Acid is one of the fatty acids that induce rapid Malassezia growth in lab settings.

It's worth noting that what feeds yeast in a lab doesn't necessarily feed it on your face since formulation and your skin's chemistry play a bigger role.

Tromethamine helps balance the pH level of a product. Normal pH level of skin is slightly acidic (~4.75-5.5). The acidity of our skin is maintained by our glands and skin biome. Being slightly acidic allows our skin to create an "acid mantle". This acid mantle is a thin barrier that protects our skin from bacteria and contaminants.

Oral Tromethanmine is an anti-inflammatory drug but plays the role of masking, adding fragrance, and/or balancing pH in skincare.

1,3-Propanediol, 2-amino-2-(hydroxymethyl)-

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!