SkinCeuticals H.A. Intensifier Multi-Glycan

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 gets a bad rep because it is irritating and drying due to its astringent property. Astringents draw out natural oils in tissue to constrict pores and dry out your skin.

However, alcohol denat. is not all that bad.

Due to its low molecular weight, alcohol denat. tends to evaporate quickly. One study on pig skin found half of applied alcohol evaporated in 10 seconds and less than 3% stayed on skin.

This also helps other ingredients become better absorbed upon application.

Studies are conflicted about whether this ingredient causes skin dehydration. One study from 2005 found adding emollients to propanol-based sanitizer decreased skin dryness and irritation. Another study found irritation only occurs if your skin is already damaged.

Small amounts of alcohol are generally tolerated by oily skin or people who live in humid environments.

The rule of thumb is this ingredient will probably not affect your skin much if it is near the end of an ingredients list.

One thing to note:
People with ALDH2 (aldehyde dehydrogenase 2) deficiency may experience skin irritation from continued alcohol use. About 8% of the world's population have this deficiency.

The Cosmetic Ingredient Review Expert Panel has determined denatured alcohols to be safe for use in concentrations between 0.05% and 12% (depending on which denaturant is used).

Also...

This ingredient has antimicrobial and solvent properties.

The antimicrobial property helps preserve products and increase their shelf life. As a solvent, it helps dissolve other ingredients.

Look for formulas that contain glycerin, hyaluronic acid, or panthenol if you want to offset any drying effect.

This ingredient will trip away your skin's natural oils/lipids that help it lock in moisture. This can worsen dryness, trigger eczema flare-ups, and aggravate rosacea.

Be sure to patch test any product with this ingredient if you have dry or sensitive skin, eczema, or rosacea.

This ingredient helped skin make more of its own natural “water-holding” molecules (called GAGs) in lab studies and skin models, which are important for keeping skin plump and hydrated. It also supported proteins that help anchor and support the skin’s layers.

Most human studies look at full skincare formulas rather than the ingredient on its own.

In one 12-week study, a facial serum containing Pro-Xylane was linked to improvements in skin hydration, firmness, and the appearance of sun-damaged skin.

In a more recent study, a product with hydroxypropyl tetrahydropyrantriol plus niacinamide was used after laser treatments and showed visible improvements in fine lines, wrinkles, and overall skin appearance within about 8 weeks, along with signs that the skin was calming and repairing itself.

The CIR Expert Panel has confirmed this ingredient to be nontoxic and clinical studies show no sensitization at cosmetic use concentrations.

True allergic reactions are quite rare: a 15-year retrospective study of 6,751 patients found only 0.31% had a positive reaction (and less than half were considered clinically relevant).

It seemed that when sensitization does occur, it's most commonly linked to topical medication (like corticosteroids) and not cosmetics. Allergic contact dermatitis also appears largely limited to individuals with underlying skin conditions.

Overall, propylene glycol is a well-studied ingredient that most people can tolerate without issue.

One component, glabridin, has extra potent antioxidant and soothing properties. It has also been found to block pigmentation from UVB rays in guinea pigs.

Licorice Root also contains a flavonoid. Flavonoids are a natural substance from in plants. Flavonoids also have antioxidant properties.

Another component, glycyrrhizin, has been found to have anti-inflammatory and antimicrobial benefits. This may make licorice root extract effective at treating acne. However, more research is needed to support this.

Liquiritin is one of the flavone compounds found in licorice. It has been found to help lighten skin by preventing tyrosinase from reacting with tyrosine. When the two react, protein is converted to melanin. Melanin is the substance in your body that gives your features pigmentation.

Licorice root is native to Southern Europe and Asia. It has been used in traditional Chinese medicine to help with respiratory issues.

The isoflavones are the workhorses behind the common claims; lab and animal studies show they mop up free radicals, help protect skin cells from UVB damage, and nudge fibroblasts to make more collagen while slowing the enzymes that break collagen down.

One controlled clinical study using an isoflavone cream reported softer wrinkles and better skin texture over time. A topical fermented soy extract also improved hydration and elasticity in an animal aging model.

The big caveat is that most of this evidence comes from soy isoflavones and related fermented soy extracts rather than this exact INCI. Some of the strongest data also comes from oral studies.

So it's best to think of this ingredient as a gentle, antioxidant-leaning conditioning agent rather than a proven wrinkle eraser.

At this time, there's no published concentration levels for this specific ferment but it usually shows up at modest levels in real products (~1% or less).

One last thing for people with soy allergies: it's always worth patch testing this ingredient despite the lowered allergy risk.

Interestingly, the size of the molecule affects its behavior:

Some clinical evidence links low molecular weight versions to improved wrinkle depth, elasticity, anti-inflammatory effects, and barrier repair.

Many serums use a blend of both weights so you can get surface hydration plus longer-lasting and deeper effects.

You'll typically see concentrations between 0.1-2% for this ingredient.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.

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.

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.

Like salicylic acid, this ingredient is a chemical exfoliant that can help break down the oil in your pores and reduce inflammation.

Though studies for LHA do show it to be less effective than salicylic acid. To be fair, salicylic acid is the reigning monarch of acne treatments.

However, a study from 2009 found LHA to be comparable to BPO, making it a good alternative for people with sensitive skin. Another study of 14 patients found a significant decrease in comedones after using LHA.

Another pro of LHA? It is less irritating than salicylic acid due to its large molecule size.

Large molecules cannot penetrate skin as well, so they are gentler on the skin. LHA is much less penetrative than salicylic acid.

An in-vitro study (not done on a living organism) found only 6% of LHA penetrated past the statum corneum compared to 58% of salicylic acid. An in-vivo (done on a living organism) analysis revealed ~17% of LHA was still present in the top layer of skin after 4 days, versus ~9% of salicylic acid.

Interestingly, a study from 2008 found LHA comparable to another famous acid, glycolic acid.

This study found about 10% of LHA is as effective as 20-50% of glycolic acid in treating hyperpigmentation and fine-lines.

Hydroxy acids have been found to stimulate skin protein, lipids, and thermal thickening. This may have anti-aging benefits.

You'll likely see this in many BHA products because this is the go-to solvent for salicylic acid.

This ingredient is typically used at levels between 2-20%.

Regarding fungal acne:
In 2019, this ingredient was tested against multiple Malassezia species (the yeast that causes fungal acne) and showed no growth.

Typical usage levels in cosmetics are usually low and in the range of 0.015 - 2.3%.

You'll typically find it at 0.5-3% in formulations. It's also often paired with its sibling, Methyl Glucose Sesquistearate, to create stable and mild emulsion systems.

The yeast that causes fungal acne loves fats and oils with a carbon chain length between 11 and 24. This ingredient contains stearic acid, which has a chain length of 18. Due to this, we mark this ingredient as not safe for fungal acne.

Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).

Xanthan gum is a pretty common and great ingredient. It is a natural, non-toxic, non-irritating ingredient that is also commonly used in food products.

Read about common types of Hyaluronic Acid here:

In cosmetics, it mainly functions as a bulking agent, viscosity controller, binder, and absorbent. It helps thicken products, stabilize powders, and get certain textures a less "wet" feel.

This ingredient has a pretty solid safety profile; it's recognized as a safe food additive and its large molecular size means it doesn't meaningfully penetrate skin.

Human repeat insult patch tests using a rinse-off facial product containing 42.69% dextrin found no skin irritation or sensitization in 54 subjects.

Typical real-world usage is much lower: usually under 1% as a texture modifier and up to 40% in masks (rinse off products use less).

It can also form a thin protective film on skin. One study found that a formula using this polymer helped slow down how quickly other ingredients (like DEET) were absorbed through skin.

A 2024 study of over 1,300 patients confirmed that sensitization to this ingredient is rare. It is also non-mutagenic and has a clean track record.

A study from 2002 found rice to help increase the rate of wound healing. The same study found an improvement of skin barrier function in the patients after taking rice baths.

Numerous in-vitro studies have found rice water to help decrease sun damage by increasing collagen production and inhibiting the process of tyrosinase.

Long story short- tyrosinase is an enzyme that controls melanin production. Our bodies start producing melanin (AKA tanning) when exposed to UV radiation to protect against damage. Rice water is found to partially block this process.

Though more research is needed on rice's ability to help with UV protection, recent studies seem promising.

Wondering why rice is hydrating? The protein in rice have emollient properties. Emollients create a barrier on the skin to trap moisture in, keeping your skin moisturized.

Some rice extract may have mildly-exfoliating properties. These are mainly limited to Oryza Sativa (Rice) Bran and Oryza Sativa (Rice) Germ Powder.

This rice was first cultivated in China over 10,000 years ago. Many cultures throughout Asia have used rice water on skin and hair for centuries.

In practice, that translates to a long shelf life and a consistently elegant skin feel.

While there is an assumption Caprylic Triglyceride can clog pores due to it being derived from coconut oil, there is no research supporting this. Just patch test if you have concerns.

Fractionated coconut oil and MCT Oil are both listed as Caprylic/Capric Triglyceride according to INCI. This is because INCI names are based on the ingredient’s final chemical composition and not its marketing name or source.

This ingredient is treated as the gold standard fungal acne safe oil. Even though it is coconut derived, the problematic lauric acid is stripped out.

This leaves just caprylic (C8) and capric (C10) acid. These chain lengths actually trend antifungal; a 2020 study found caprylic acid was enough to disrupt Malassezia furfur cell membrane, with a caprylic acid derivative damaging membrane structures at concentrations as low as 0.2%.

Your skin has cells called fibroblasts that build collagen (the stuff that keeps skin firm and smooth). Adenosine basically flips a switch on these cells that tells them to get to work making more collagen and other proteins. These cells slow down on their own as skin ages, so Adenosine helps give them a little nudge to keep going.

The clinical backing is pretty solid too.

A blind, randomized, placebo-controlled trial of 126 women aged 45-65 tested a 0.1% cream twice daily and found real improvements in crow's feet and frown lines using a precise 3D skin-mapping technique; these changes showed up by week 3 and held at 2 months.

A later study using Adenosine-loaded dissolving microneedle patches reported gains in wrinkle depth, dermal density, elasticity, and hydration.

On concentrations, South Korea's Ministry of Food and Drug Safety has set 0.04% as the approved functional anti-wrinkle level. You'll typically see this ingredient used somewhere in the 0.04-0.1% range since it works at low doses.

This ingredient has been found safe for cosmetics with the data showing no irritation or sensitization.

Overall, this is a great ingredient for any anti-aging routine and has no photosensitizing effect, so it suits both AM and PM use.

On the safety side, the Cosmetic Ingredient Review Expert Panel has concluded this ingredient to be safe as used in current cosmetic practices + concentrations.

Typical use levels in a formula run about 1-5%.

Like other essential oils, this ingredient can be a fragrance allergen.

Limonene acts as an antioxidant, meaning it helps neutralize free radicals.

When exposed to air, oxidized limonene may sensitize the skin. Because of this, limonene is often avoided by people with sensitive skin.

The term 'fragrance' is not regulated in many countries. In many cases, it is up to the brand to define this term. For instance, many brands choose to label themselves as "fragrance-free" because they are not using synthetic fragrances. However, their products may still contain ingredients such as essential oils that are considered a fragrance.

As an antioxidant, it helps fight free-radical molecules. Free-radical molecules are capable of damaging our cells and other genetic material. Thus, antioxidants may reduce the signs of aging.

This ingredient is oil-soluble.