maru.derm Shower Gel

Being created from coconut oil means Cocamidopropyl Betaine is hydrating for the skin.

While Cocamidopropyl Betaine was believed to be an allergen, a study from 2012 disproved this. It found two compounds in unpure Cocamidopropyl Betaine to be the irritants: aminoamide and 3-dimethylaminopropylamine. High-grade and pure Cocamidopropyl Betaine did not induce allergic reactions during this study.

You might see people debate whether Sodium Chloride is comedogenic, but there actually haven't been any comedogenic tests done on it. Either way, the overall formulation of a product matters a lot more than any single ingredient.

You might see this ingredient used in scrubs as a primary exfoliating ingredient.

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 lactic acid molecules are larger than glycolic acid, they don’t penetrate as deeply. This means they’re less likely to sting or irritate, making it a great choice for beginners or those with sensitive skin.

Like glycolic acid, it can:

Lactic acid also acts as a humectant (like hyaluronic acid). It can draw water into the skin to improve hydration and also plays a role in the skin's natural moisturizing factor (NMF) in the form of sodium lactate.

Studies show it can boost ceramide production to strengthen the skin barrier and even help balance the skin’s microbiome.

To get results, choose products with a pH between 3-4.

Lower strengths (5-12%) focus on surface exfoliation; higher strengths (12% and up) can reach deeper in the dermis (deeper, supportive layer) to improve skin texture and firmness over time.

Though it was originally derived from milk, most modern lactic acid used in skincare is vegan. It is made through non-dairy fermentation to create a bio-identical and stable form suitable for all formulations.

When lactic acid shows up near the end of an ingredient list, it usually means the brand added just a tiny amount to adjust the product’s pH.

Legend has it that Cleopatra used to bathe in sour milk to help reduce wrinkles.

Lactic acid is truly a gentle multitasker: it exfoliates, hydrates, strengthens, and brightens. It's a great ingredient for giving your skin a smooth, glowing, and healthy look without the harshness of stronger acids.

Read more about some other popular AHA's here:

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.

It is derived from stearic acid, a natural fatty acid commonly found in vegetable oils and animal fats.

Glycol Distearate isn't fungal acne safe.

As an emulsifier, Peg-7 Glyceryl Cocoate prevents ingredients such as oils and water from separating. It also helps rinse away oils, dirt, and pollutants from skin.

Peg-7 Glyceryl Cocoate may not be fungal acne safe. It can also dry out skin.

Typically, it's used in cosmetic products to protect them from deterioration caused by UV rays. This is why you'll find it in a lot of products that aren't sunscreens.

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.

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 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.

Glycolic acid removes the top layer of dead skin cells to allow newer and fresher ones to emerge.

AHAs work by breaking down the structural “glue” that holds old skin cells in place. When that buildup is gone, your skin can renew itself more efficiently.

Research also shows glycolic acid stimulates collagen production, helping to firm and thicken the skin over time. This is one of its biggest advantages over other AHAs.

Overall, glycolic acid helps with:

Fun fact: Glycolic acid boosts skin hydration by helping it produce molecules that increase hyaluronic acid naturally.

To work best, glycolic acid products should have a pH between 3-4 (that’s where exfoliation is most effective but still gentle on skin).

The pH and concentration of a product are key to its effectiveness:

It is normal to feel a slight stinging sensation when using glycolic acid. This usually fades as your skin adjusts.

Because glycolic acid has the smallest molecular size in the AHA family, it can penetrate deeper, which enhances its effectiveness but also makes it more likely to irritate sensitive skin.

If your skin is very sensitive or prone to rosacea, glycolic acid may be too strong; in that case, try milder options like lactic acid or a PHA instead.

Recent studies suggest glycolic acid might even help protect against UV damage. But don’t skip sunscreen! Freshly exfoliated skin is more sensitive to the sun.

Glycolic acid is a skincare superstar. It smooths, brightens, hydrates, and firms the skin. Unless you’re highly sensitive, it’s well worth adding to your routine.

Read more about some other popular AHA's here:

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

Tartaric acid is not as well studied as other AHAs, such as glycolic acid.

Like other AHAs, malic acid gently removes the top layer of dead skin cells to reveal smoother, brighter skin underneath.

Though it’s considered milder and less potent than glycolic or lactic acid, it can help improve:

Due to its larger molecular structure, it penetrates the skin more slowly and is often used in combination with other AHAs to enhance their overall effectiveness.

Malic acid often plays a role in balancing a product’s pH and is usually included in small amounts (around 1-2%) as a supporting exfoliant.

As with all exfoliating acids, you should wear sunscreen daily when using malic acid to protect your newly resurfaced skin.

Fun fact: Malic acid is the compound responsible for the tart flavor of apples and other sour fruits.

While research on malic acid is limited compared to glycolic or lactic acid, it’s still a safe and mild exfoliant.

Read more about some other popular AHA's here:

High percentages of Sodium Lactate can have an exfoliating effect.

Fun fact: Sodium Lactate is produced from fermented sugar.

Last, the phytochemicals found in apples are strong antioxidants. These antioxidants help with anti-aging as they protect your skin cells against oxidative damage.

And of course, lemons are rich in Vitamin C. Vitamin C helps with skin-brightening and increasing collagen production.

The acidity of lemons may work as an astringent for acne.

However, lemons can also cause skin sensitivity due to its limonene content. It can also increase photosensitivity, or sensitivity to the sun.

This ingredient is also used to add a lemon scent to products.

Vaccinium Myrtillus Fruit Extract also helps reduce irritation.

Glycolic acid is a derivative of sugarcane. While glycolic acid is an AHA with exfoliating properties, sugarcane is not an AHA.

A study from 2021 found the compounds in sugarcane extract to have antioxidant, antimicrobial, and anti-inflammatory activity. The study also suggests these compounds can inhibit skin ageing enzymes and promote collagen synthesis.

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.

The FDA requires batch-to-batch certification for this ingredient that is held to a pretty rigorous standard. That means the CI 17200 in your cosmetics has been tested and approved before it ever reaches you.

Contact allergy to cosmetic-grade dyes used at low concentrations are uncommon but has been documented before.

This ingredient also goes by the name D&C RED NO. 33.

CI 17200 has a comedogenic rating of 1 and an irritancy rating of 2 on a scale of 0-5. This is based on peer-reviewed research from the man who invented the comedogenic scale.

A 1 on the comedogenic scale is about as low as it gets without being a flat zero, and makes sense for CI 17200.

It's a water-soluble dye used at very small concentrations (typically 0.001-0.1%), so it dissolves into the water phase of a formula rather than sitting on your skin the way an oil or wax would.

The irritancy rating of 2 reflects that, like most synthetic dyes, there's a small possibility of mild irritation ( particularly for people with existing dye sensitivities).

For the vast majority of people, it's a non-issue at typical use levels.

It's also worth keeping in mind that comedogenic and irritancy ratings are tested on individual ingredients, not finished formulas. The final product's formulation, concentration, and other ingredients all play a role in how something actually behaves on your skin.

Just so you know, the FDA ban on Red Dye No. 3 refers to CI 45430, not this ingredient. CI 45430 and CI 17200 are different chemical compounds with distinct safety and regulatory histories.

It's also worth noting that Red No. 3 (CI 45430) was already banned from cosmetics back in 1990, so the 2025 action just extended the ban to food and oral drugs. CI 17200 was never part of any of this.

Research on a hydrogel with serine confirmed this serine got delivered to your stratum corneum and demonstrated enhanced skin moisturization.

Interestingly serine also helps your skin produce filaggrin, a protein that keeps your skin barrier strong and used to create collagen.

This ingredient can either be derived from an animal product or be synthetically created.

Reviews of this ingredient have found it to be neither a dermal irritant nor a sensitizer.

Fun fact: Proline can be found in protein-rich foods like meat, fish, eggs, and dairy.

One study found histidine and carnosine to be a dynamic duo for your skin:

Oral histidine has also been found to help with filaggrin-deficit skin disorders such as atopic dermatitis.

Why is it considered a semi-essential amino acid? This is because adults are able to create it but children must get it from their diet.

Two structures of phenylalanine exist: L-phenylalanine and D-phenylalanine. L-phenylalanine is essential, this means our bodies cannot produce it naturally and we must get it from foods. Our bodies convert D-phenylalanine to neurotransmitters, and D-phenylalanine is found in our bodies naturally.

Some foods that contain L-phenylalanine include eggs, soybeans, beef, milk.

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.