MEDI-PEEL Peptide 9 Aqua Essence Toner

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.

Some studies suggest betaine may support making skin tone more even.

Fun fact: Betaine naturally exists in the skin and the body. In cosmetic products, it can be either plant-derived (most commonly from sugar beets) or synthetically produced for consistency and stability.

Betaine is also known as trimethylglycine.

Due to its antioxidant properties, trehalose may help with signs of aging. Antioxidants help fight free-radical molecules, unstable molecules that may damage your skin.

In medicine, trehalose and hyaluronic acid are used to help treat dry eyes.

Some animals, plants, and bacteria create trehalose as a source of energy to survive freeze or lack of water.

This ingredient is not irritating or sensitizing. Recent research also suggests it may have skin-brightening effects through tyrosinase inhibition.

Basically, Peg-60 Hydrogenated Castor Oil helps hold ingredients together.

Here's an interesting thing about Arginine: your skin converts it into urea through the Krebs-Henseleit urea cycle. Urea is one of the most effective humectants your skin naturally produces.

A clinical study showed applying 2.5% arginine hydrochloride to atopic dermatitis skin showed significant urea levels in the stratum corneum and improved moisture in just four weeks.

Arginine is also a precursor to nitric oxide; nitric oxide improves microcirculation and supports wound healing and collagen synthesis.

One study found that an amino acid complex containing Arginine reduced skin irritation, improved hydration, and accelerated skin repair in clinical / in-vivo studies.

Arginine itself is an amino acid and not a fatty acid, oil, or ester. On its own, it's not a direct food source for Malassezia, or the yeast that causes fungal acne.

A high amount of carbomer can cause pilling or balling up of products. Don't worry, most products contain 1% or less of carbomer.

This ingredient has skin conditioning, anti-inflammatory, and humectant properties. Humectants help hydrate your skin by drawing moisture from the air. This helps keep your skin moisturized.

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

Studies have found adenosine may also help with wound healing.

In skincare products, Adenosine is usually derived from yeast.

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.

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.

This ingredient is water-soluble.

The small peptides and amino acids (including Natural Moisturizing Factor components like Hydroxyproline, Serine, and Aspartic Acid) help the surface of the skin hold onto water, feel softer, and look temporarily plumper.

This ingredient also has mild film-forming and antioxidant properties with research showing the antioxidant effect is stronger the lower the molecular weight of the peptides.

It's worth being realistic here:

Topically applied Hydrolyzed Collagen conditions the upper layers of skin rather than rebuilding the structural collagen deep in your dermis (the wrinkle-and-firmness benefits people associate with Collagen mostly come from oral supplements in studies, not topicals).

However, recent lab and skin-model work on Hydrolyzed Fish Collagen has shown promising effects on cell viability and wound healing when used as an active.

Typical concentrations range from 0.2-2%, but the percentage can go much higher in rinse-off or hair products (sometimes even above 50%).

Clinical studies on this ingredient showed no irritation, sensitization, or phototoxicity.

If you are looking for vegan collagen, it usually goes by a different INCI name like hydrolyzed soy protein. Vegan collagen is derived from yeast, bacteria, or plant sources.

The results are varied.

A study from 2021 found hydrolyzed collagen increased elasticity and improved wrinkles in 1,125 participants between age 20 and 70. Another study found increased skin thickness in participants between the ages of 45 to 59.

However, It is difficult to prove that oral collagen will end up working on your skin. Many of the studies using hydrolyzed collagen also add several vitamins and nutrients into the test mixture as well.

Further studies are needed at this time.

Hydrogenated Polyisobutene is often used as a mineral oil replacement.

Propanediol is not likely to cause sensitivity and considered safe to use. It is derived from corn or petroleum with a clear color and no scent.

As a film former, it creates a light and flexible layer on the skin's surface. This helps lock in moisture without feeling heavy.

It's typically used at concentrations up to 1.9% in leave-on products. CIR has concluded that these ingredients are safe in cosmetics at current use levels.

Due to its large molecule size, it doesn't readily penetrate into skin and mostly just sits on the surface. A large UK-based patch test study of over 1,300 patients found that sensitization to related acrylate copolymers is rare.

A follow-up clinical trial found that a topical crosslinked HA serum applied after fillers, microneedling, or chemical peels was well-tolerated and enhanced skin quality at 14 / 28 days.

More recent research suggests that concentrations as low as 0.03% can act as a penetration enhancer for other skincare actives.

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.

Other contents of chondrus crispus include polysaccharides, peptides, and amino acids. These help hydrate the skin.

What's the difference between algae and seaweed?
Algae is a broad term that includes seaweed. Not all algae is seaweed.

This ingredient can also be found in pill medicines to help our bodies digest other ingredients.

Neurotransmitter peptides are also often called "botox in a bottle". This is because these peptides have the ability to relax the muscles.

Though relaxing the muscles can prevent expression lines (as we have seen in botox), the studies do not show these peptides to be a botox replacement. The effects of this muscle relaxation is also short-term, as opposed to longer-term results from botox.

Astaxanthin is also great at soothing skin due to its ability to block molecules that signal inflammation. It is currently being studied for preventing chronic inflammatory diseases.

Plus, a study from 2012 found Astaxanthin in liposomes protected mouse skin from UV-damage.

Fun fact: Astaxanthin is responsible for giving salmon a pink color.

Because hydrolyzed hyaluronic acid is smaller in size, it can slip past your outermost layer of skin more easily than full-sized HA.

Most formulations will combine all sizes to get the best of both worlds.

Typical usage levels range from 0.01-1%. Any percentage higher than 2% might become goopy and tacky.

It's designed to mimic the collagen-stimulating activity in your skin by copying a snippet of one of your skin's own matrix proteins. This nudges fibroblasts into making more collagen while inhibiting the enzyme that breaks down skin protein.

The manufacturer's in vivo study of 45 volunteers found 1% and 2.5% reduced the appearance of wrinkles by 7% and 12% respectively, after using it twice daily for 84 days.

This is in the expected range for peptides; they're slow and cumulative actives and not overnight fixers.

Typical use levels range from 1-3% and this ingredient gets along with pretty much everything.

On the fungal acne front:
Although palmitic acid sits in the chain length that Malassezia can feed on, this ingredient has it locked in an amine bond. This makes it hard for Malassezia to access as a source of food, and therefore fungal acne safe.

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

Zhi Mu root is rich in sarsasapogenin. This compound has anti-inflammatory and soothing properties.

It is commonly used in East Asian medicine.

The comparison to Botox does have limits because the molecule is water-loving and relatively large.

Acetyl Hexapeptide-8 has a hard time absorbing deeply enough through the skin's outer barrier to actually reach the muscles.

So whether it truly works the way Botox does at a biological level is still up for debate, but early clinical outcomes are fairly encouraging.

A 12 week human study of a multi-ingredient regimen containing this ingredient saw:

While some studies have observed improvements in wrinkle appearance, it is important to note that more consistent results are seen in multi-ingredient formulations (vs just Acetyl Hexapeptide-8 alone).

Some research studies also used higher concentrations (up to 10%) while this ingredient is usually found in concentrations up to 0.005% in leave-on formulations.

While studying wound healing, researchers noticed GHK-Cu stimulated hair follicle enlargement and growth by keeping hair in its active growth phase longer. This has made it a promising ingredient for hair regrowth treatments.

Some people have reported increased facial hair. While GHK-Cu can make your hair follicles bigger, it usually doesn’t turn soft, barely-visible facial hairs into thick, dark ones.

Anecdotal reports suggest that overusing copper peptides might lead to premature aging due to excess free copper or enzyme imbalances. This claim isn’t backed by large-scale studies.

Unfortunately, there are limited human studies for this ingredient. While early results are promising, many studies are either small, in-vitro, or not rigorously controlled.

For example, there is a 1998 study that explored the effects of copper tripeptide, vitamin C, tretinoin, and melatonin on skin repair and collagen synthesis.

After one month, increased procollagen production was seen in 7 out of 10 participants using copper tripeptide (more than those using vitamin C, melatonin, or tretinoin.

While the study was exploratory, it offers early evidence that copper tripeptide may support collagen production. Larger, well-designed trials are still needed to confirm its potential and understand individual responses.

Read more about other common types of peptides here:

The only catch is that HA isn't a single thing; it actually comes in a wide range of molecular weights (~50 - 2,000+ kDA) and size matters.

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

This is why the best HA serums blend the two sizes together so you get the best of both worlds.

The majority of cosmetic HA is produced by bacterial fermentation, typically using Streptococcus or Bacillus strains. Typical use levels in skincare sit around 0.1-2%.

A clinical study using a 0.2% low-molecular weight HA gel showed improvement in facial seborrheic dermatitis with excellent tolerance.

These are some other common types of Hyaluronic Acid:

It’s considered a “next-gen” version of Argireline (Acetyl Hexapeptide-8), an older peptide with more research behind it that also supports collagen production.

SNAP-8 showed slightly better results than Argireline in one small manufacturer-funded study, but there’s limited independent research. Plus, most tests use concentrations higher than what’s typically found in skincare products.

This ingredient might offer a subtle smoothing effect but it won't don’t deliver the dramatic results of actual Botox injections.

Think of it more like a supporting actor in your skincare lineup.

This ingredient calms down a specific inflammation signal in your skin cells (called IL-6). When left unchecked, this signal triggers enzymes that break down collagen and elastin.

Clinical testing showed statistically significant improvements in:

Studies also found the more of this ingredient used, the more your skin produces Collagen I, fibronectin, and hyaluronic acid.

You'll likely see this ingredient paired with Palmitoyl Tripeptide-1 in the well-known Matrixyl 3000 complex for enhanced anti-aging effects.

A 3% concentration applied twice daily for two months showed meaningful skin rejuvenation results in clinical panels.

Fungal acne note:
Usually a palmitic acid component can feed Malassezia in unbound form, but here is is covalently bonded to the peptide. This means it is very difficult for Malassezia to access, and therefore very unlikely to cause fungal acne.

In-vitro studies show it can enhance epidermal regeneration, boost synthesis of collagen types I, III, and IV, and improved markers of skin differentiation.

Think of skin differentiation like this: your skin cells are born at the bottom and slowly travel up to the surface as they "grow up". As they move up, they start producing specific proteins that make your skin do its job well. Two of these proteins are keratin (it makes your skin tough) and filaggrin (it breaks apart into tiny molecules to keep your skin hydrated). So Hexapeptide-9 has shown to help skin cells grow up properly and make stronger, more hydrated skin.

A manufacturer also reports increased collagen production by 117% and hyaluronic acid production by 267%.

Just know much of the published data comes from manufacturer-sponsored studies. There is a recent clinical trial showing promising anti-aging results but the evidence base is still growing.

Generally, this ingredient is well-tolerated and there's no harm in using it as a supportive ingredient in your routine.

Read more about other common types of peptides here:

Once there, it acts as a matrikine, a signaling peptide that prompts fibroblasts to produce more collagen, fibronectin, and hyaluronic acid.

In vitro studies show it can boost collagen production in skin cells even when UV-damaged skin samples were treated with it at a tiny concentration (it almost fully restored dermal collagen at 5ppm). It achieved this at 100x lower concentration than retinoic acid, which needed 500 ppm to do the same thing.

Human clinical data is promising, but modest:

A study of 23 female volunteers found a small but statistically significant increase (~4%) in skin thickness after treatment at 4 ppm.

A separate small trial of 15 women showed statistically significant reductions in wrinkle length, depth, and skin roughness after applying it twice daily for four weeks.

You'll likely see Pal-GHK paired with Palmitoyl Tetrapeptide-7 as part of the Matrixyl 3000 complex.

Fungal acne note:
Usually a palmitic acid component can feed Malassezia in unbound form, but here is is covalently bonded to the peptide. This means it is very difficult for Malassezia to access, and therefore very unlikely to cause fungal acne.

A 12 week clinical study found that a moisturizer containing just 3 ppm of Matrixyl led to a significant improvement in fine-lines and wrinkles. Another study showed an 18% reduction in wrinkle depth, 37% reduction in wrinkle thickness, and a 21% improvement in skin firmness after just 28 days of twice-daily use.

The coolest part is that it works at incredibly low concentrations (like 0.0003%) and it plays well with other actives.

The CIR (Cosmetic Ingredient Review) panel found it to be non-sensitizing across multiple tests and human patch tests also showed no irritation or sensitization.

Fun fact: Matrixyl was originally developed by French company Sederma and Procter & Gamble.

Read more about other common types of peptides here: