By Terry Baume de Rose Hydrating Sheet Mask

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.

Yes! This ingredient comes from the seeds of a tree. The name 'Locust Bean Gum' can be misleading.

D-panthenol is also known as dexpanthenol. Most cosmetics use dexpanthenol or a mixture of D and L-panthenol.

Panthenol is famous due to its ability to go deeper into the skin's layers. Using this ingredient has numerous pros (and no cons):

Like hyaluronic acid, panthenol is a humectant. Humectants are able to bind and hold large amounts of water to keep skin hydrated.

This ingredient works well for wound healing. It works by increasing tissue in the wound and helps close open wounds.

Once oxidized, panthenol converts to pantothenic acid. Panthothenic acid is found in all living cells.

This ingredient is also referred to as pro-vitamin B5.

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.

This ingredient is considered hypoallergenic and non-toxic. Cellulose Gum can be found in cosmetics, food, and other household goods such as paper products.

These compounds allow centella to dial back inflammation, encourage the skin to build and hold onto collagen, support the barrier and hydration, and bring solid antioxidant activity to protect against signs of aging.

Centella also carries a nice supporting cast of Vitamin A, vitamin C, several B vitamins, and amino acids. Put it all together and you get an ingredient that soothes, hydrates, and protects, all at once.

Most of centella's magic comes from the four big compounds (Asiaticoside, Madecassoside, Asiatic Acid, and Madecassic Acid). These are the actives doing the heavy lifting in almost every centella study.

Here is the short version of what they do in the skin:

So it is not just soothing for the sake of soothing. Centella calms the skin AND helps it rebuild.

Just FYI, not all centella on an ingredient list is the same. What you are getting actually depends on the extract:

Fun fact on the ratios: the leaves tend to be richest in Madecassoside and Asiaticoside, and lower in the two acids. The exact amounts shift with where the plant is grown and how it is processed. This means purity really does vary brand to brand.

Centella is one of the most easygoing actives out there.

It layers well with basically everything: niacinamide, hyaluronic acid, peptides, and vitamin C, and also pairs nicely with stronger actives like retinoids and exfoliating acids where it can help take the edge off irritation.

On the safety side, centella and its triterpenes are classified as weak sensitizers, meaning allergic reactions are possible but uncommon.

Patch tests at 1% and 5% came back negative in test panels, and creams at typical use levels did not cause allergic reactions across large groups of people.

But as with any new active, a patch test is still a smart move for very reactive skin.

Centella is widely used because it is effective at low percentages. For context, human safety testing found no meaningful irritation from creams containing centella extract at everyday use levels (the tested amounts were well under 1%).

The irritancy threshold in animal testing was also above 30% (so real-world formulas sit far below anything concerning).

In collagen lab studies, higher concentrations drove more collagen synthesis, so serums built around centella tend to feature it more prominently.

Bottom line: you will find centella working nicely anywhere from a fraction of a percent up to hero-ingredient levels depending on whether it is a supporting soother or the main event.

Fun fact: Centella has been used as a medicine and in food for many centuries. As a medicine, it is used to treat burns, scratches, and wounds.

Ancient Chinese medicine has used peony root to treat dark spots, but studies are looking into this claim more.

Antioxidant components in chamomile make it an effective ingredient to help slow the signs of aging. Antioxidants help fight free-radical molecules, or molecules that may damage your skin.

Essential oils from chamomile have been found to improve wound healing due to its antimicrobial properties.

Ancient Greeks and Egyptians used Chamomile to treat skin redness and dryness. Chamomile has also been used to help treat stomach issues.

As a co-emulsifier, its "head" and "tail" sit at the oil-water interface. But overall, the short C8 tail and not being water soluble means it doesn't really have the muscle to emulsify a formula on its own. That's why you'll often see it paired with a primary emulsifier like Cetearyl Glucoside.

Interestingly, Glyceryl Caprylate acts as a preservative booster. This is because its fatty-acid backbone disrupts microbial lipid membranes. It shows excellent activity against bacteria and yeast but is weaker against mold.

Typical concentrations range from 0.5-1% and this ingredient is generally non-irritating.

Because this ingredient has a C8 fatty acid chain, it is outside the range that the Malassezia yeast metabolizes (making it fungal acne safe).

Concentrations up to 100% in guinea pig tests found it to be non-sensitizing and completely safe for use in cosmetics.

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

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%.

For instance, Habanolide is a proprietary trade name for a specific aroma chemical. When used as a fragrance ingredient in cosmetics, most aroma chemicals fall under the broad labeling category of “FRAGRANCE” or “PARFUM” according to EU and US regulations.

The term 'parfum' or '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 by INCI standards.

One example is Calendula flower extract. Calendula is an essential oil that still imparts a scent or 'fragrance'.

Depending on the blend, the ingredients in the mixture can cause allergies and sensitivities on the skin. Some ingredients that are known EU allergens include linalool and citronellol.

Parfum can also be used to mask or cover an unpleasant scent.

The bottom line is: not all fragrances/parfum/ingredients are created equally. If you are worried about fragrances, we recommend taking a closer look at an ingredient. And of course, we always recommend speaking with a professional.

It's actually inactive on its own and works like a slow-release "storage" form; the enzymes in your skin called esterases gradually convert it into active vitamin E over time.

One in vivo study showed 5% of the acetate in the living layer of the epidermis converted to vitamin E after 5 days of application. This study also found the skin gained protection against UV damage even though the conversion was slow and small.

Once converted, vitamin E acts as a skin's main fat-soluble antioxidant that fights free radicals to protect skin from damage.

Topical vitamin E generally boosts the skin's photoprotection, and it reduced UV-damage in animal models.

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.

Overall, it has a pretty solid safety profile and has been found to be non-irritating and non-comedogenic. Allergic reactions may happen but stay rare due to how widely the ingredient gets used.

The concentration will vary depending on the formula; industry data shows 0.1% in baby lotions, 3% in lipsticks, and 5% in foot powders. You can also find this ingredient at 100% in a pure vitamin E oil.

Most leave-on skincare keeps it at the lower end, often between 0.5-1%.

Safety-wise, this ingredient is pretty solid; it's even recognized as a food additive. Both animal and clinical studies found no adverse effects at the levels used in cosmetics.

Industry data shows this ingredient is used up to 45.7% in spray products and up to 33% in powder products.

Geraniol can be found in many essential oils including Rose Oil and Citronella Oil. The scent of Geraniol is often described as "rose-like". Many foods also contain Geraniol for fruit flavoring.

Geraniol can irritate the skin when exposed to air. However, irritation depends on the ability of geraniol to penetrate into the skin. In general, geraniol is not able to penetrate skin easily.

Geraniol is colorless and has low water-solubility. However, it is soluble in common organic solvents.

Like citronellol, it is a natural insect repellent.

2,6-Octadien-1-ol, 3,7-dimethyl-, (2E)-

A 2024 review found evidence for the Rosa canina species supports its use for scarring, hyperpigmentation, wrinkles, and atopic dermatitis; this was mostly credited to its vitamin C content and fatty acid composition as the primary active mechanisms.

You might see this ingredient marketed as a "natural retinol". Some rosehip seed oils contains traces of all-trans-retinoic acid but these trace amounts are far below biologically active levels.

The Cosmetic Ingredient Review Panel has deemed this ingredient safe and it's well-tolerated.

Fungal acne: The fatty acids of this oil fall into the C11-24 range that Malassezia yeast can metabolize, so this ingredient may not be fungal acne safe.

Squalene is also naturally present in olive oil and exhibits moisturizing and antioxidant properties.

The polyphenols in olive oil also show anti-aging promise; one clinical study found a measurable improvement in skin appearance after 30 days of topical serum use.

Just be aware that applying olive oil directly to skin can weaken the barrier and cause redness. One study with volunteers found even people without sensitive skin experienced a significant reduction in stratum corneum integrity and induced mild erythema.

It's best to use this ingredient as part of a carefully crafted formula (instead of putting it on skin directly from the bottle).

Because it has a 2-3 on the comedogenic scale, it is a moderate risk for acne-prone skin. However, the overall formulation of a product matters more than a few ingredients with comedogenic ratings.

This ingredient may not be fungal acne safe because of the oleic and palmitic acid content. These fall within the C11-24 fatty acid range that the Malassezia yeast can metabolize to grow.

Overall, olive oil is a well-studied and nourishing skincare ingredient.

Other major parts of Rose Oil include citronellol and geraniol. Both of these are known EU allergens and cause contact-allergies.

The downsides of this ingredient outweight the positives.

Just keep in mind that rose extracts contain known fragrance allergens like citronellol, geraniol, linalool, and limonene.

Rosa Damascena Extract is a tonic. Tonics are used to remove soap residues. They also help moisturize the skin.