Geek & Gorgeous Happier Barrier

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.

Because this ingredient mimics the natural oils in your skin, it helps keep your barrier healthy and hydrated.

The manufacturer's tests found:

Typical use concentrations range from 2-3% and it works across a pH of 4.5-8.5.

This ingredient has been found safe to use in cosmetics and has a low irritation profile.

Because it's build on stearic acid, it may not be fungal acne safe. Stearic acid is a C18 fatty acid that falls within the range (C11-24) that Malassezia can feed on.

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.

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.

Unlike other plant oils, jojoba wax doesn't easily penetrate skin. It mostly works in the uppermost layers as an emollient. This just means it forms a light barrier on the skin to help retain moisture.

Formulations with jojoba esters up to 90% reduced transepidermal water loss (TEWL) and increased barrier recovery by 81% (outperforming bisabolol at 47%).

Besides barrier support, the science also suggests jojoba to have anti-inflammatory effects and potential applications for skin infections, aging, and wound healing.

Fun fact: Indigenous cultures have used jojoba as a moisturizer and to help treat burns for centuries.

Due to its fatty acid content, Jojoba oil may not be fungal acne safe.

Specifically, saccharide Isomerate is a humectant. Humectants draw moisture from the air to our skin.

Research shows Saccharide Isomerate to be an effective moisturizer.

Studies show green tea extract and its catechins (like epigallocatechin gallate (EGCG)) help your skin cells product energy more efficiently and reducing the number of free-radicals that can damage your skin from the inside.

In lab-grown skin models, this translated to younger, healthier, and stronger skin.

There's also good sun protection data; researchers saw less DNA damage and redness on human skin when green tea was applied before UVB exposure. And the more they applied, the better the protection.

Needless to say, this ingredient shouldn't replace your sunscreen. But it is a great supportive ingredient that you can already find in many sunscreens and antioxidant serums.

A 2009 study found a 2% green tea lotion was effective for mild-to-moderate acne thanks to its anti-inflammatory and mild antimicrobial activity.

The quality of the extract matters a lot here:

Good extracts contain 50-90% catechins while lower quality ones are mostly there for marketing. We recommend reaching out to the brand if you have questions about the quality or source of their ingredients.

Human Repeated Insult Patch Testing showed no irritation or sensitization at use concentrations (0.86% in leave-on products and up to 30% as leaf water).

A clinical study found that applying 0.5% bisabolol daily for 8 weeks produced an average 9% decrease in skin pigmentation. Researchers found it can also suppress the process that leads to excess melanin production in skin.

In vitro studies found that bisabolol combined with propylene glycol significantly increased skin permeability by increasing lipid fluidity in the stratum corneum.

You'll likely see use concentrations quite low, usually 0.1-0.2%.

Overall, this is a well-tolerated ingredient that works well in formulas designed for sensitive, reactive, or post-procedure skin.

Research shows it can encourage your skin cells to turn over and renew by stimulating keratinocyte and fibroblast proliferation.

It also has mild keratolytic properties to help loosen and shed dead skin cells without being harsh.

Studies also suggest allantoin can help calm inflammation by dialing down some of the chemical signals your skin sends out when it is irritated.

This ingredient is typically used in the 0.1-0.5% range, and the FDA recognizes it as a skin protectant in OTC products up to 2%.

Overall, allantoin is a wonderful addition to most routines; it is stable across a wide pH range (~4-8), works well with other ingredients, and is considered non-sensitizing/non-irritating.

Fun fact: Allantoin is naturally occurring in comfrey root, beets, chamomile, and wheat sprouts. Our bodies even produce it as a byproduct of uric acid metabolism.

Ceramides are an important building block for our skin barrier. A stronger barrier helps the skin look more firm and hydrated. By bolstering the skin ceramides act as a barrier against irritating ingredients. This can help with inflammation as well.

If you would like to eat ceramides, sweet potatoes contain a small amount.

Read more about other common types of ceramides here:
Ceramide AP
Ceramide EOP
Ceramide NP

Research highlights its role in antioxidant activity, anti-inflammatory effects, skin barrier protection, and wound healing support.

In vivo research has shown that transepidermal water loss (TEWL) caused by irritant exposure can be reverse with squalene supplementation (pointing to barrier recovery support).

Its antioxidant activity is backed by ex vivo and cell-based evidence showing it can scavenge free radicals but large-scale human clinical trials isolating this effect remain limited.

One study found squalene regulated proinflammatory behavior in ways relevant to wound healing, and in vitro fibroblast studies also shows it stimulates cell migration which is a key step in skin repair.

There's just one nuance to know about this ingredient:

Squalene is particularly vulnerable to oxidation; it breaks down from UV exposure 10x faster than the other lipids on your skin's surface. The byproducts of that breakdown can clog pores and trigger inflammation, potentially worsening acne.

This is why squalene is often hydrogenated into its stable counterpart: squalane (with an "a"). Most great formulations will have alreadu kept this in mind.

Squalene has shown no significant clinical evidence of sensitization and is a great hydrating ingredient.

Research on phytosterols show they can help with skin barrier recovery and protect skin against UV-induced damage when combined with ceramides.

The fatty acid portion of this ingredient is mainly oleic acid and palmitoleic acid, two potential Malassezia triggers. Be sure to patch test if you're unsure.

They work by fitting perfectly into your stratum corneum's lipid matrix since they're structurally similar to cholesterol. Here, they reinforce your skin's barrier.

One small in vivo human study showed topical soybean phytosterols sped up barrier recovery within three days on tape-stripped skin.

Broader research credits them with:

Formulation use typically sit under 5%.

Testing in soy-allergic subjects found no sensitization signals, but be sure to patch test if you are unsure or have existing allergies.

Topically applied tocopherol has been shown to protect against UV damage by ramping up the skin's own natural defense enzymes.

It also acts as a skin conditioning agent; some studies show that regular topical use can improve the skin's water-binding capacity over 2-4 weeks.

This ingredient is especially loved for being a team player. When combined with Vitamin C, the photoprotective effect of both ingredients roughly doubles and the combo also helps reduce UV-induced DNA damage.

This ingredient has some brightening potential but it's more of a prevention ingredient than spot-fader. Cell studies show it can slow down melanin production but it's worth noting that it's not the most powerful brightener out there.

In formulations, it also serves as a stabilizer that helps protect other oxidation-prone ingredients from degrading.

Concentrations usually range from 0.1-1% in most leave-on products.

Tocopheryl Acetate is commonly found in both skincare and dietary supplements.

However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.

Due 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.

In skincare formulas, citric acid can:

While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.

Most 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.

Read more about some other popular AHA's here:

The acidity of our skin is maintained by our glands and skin biome; normal pH level of skin is slightly acidic (~4.75-5.5).

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.

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