K18 Hair PEPTIDE PREP™ pH Maintenance Shampoo Versus L'Oréal Professionnel Metal Detox Sulfate-Free Shampoo

K18 Hair PEPTIDE PREP™ pH Maintenance Shampoo Versus L'Oréal Professionnel Metal Detox Sulfate-Free Shampoo

What's inside

Key Ingredients

Benefits

Concerns

Ingredients Side-by-side

Water

Sodium C14-16 Olefin Sulfonate

Cocamidopropyl Betaine

Sodium Methyl 2-Sulfolaurate

Sodium Lauryl Sulfoacetate

Sh-Oligopeptide-78

Panthenol

Glycerin

Sodium Phytate

Guar Hydroxypropyltrimonium Chloride

Disodium 2-Sulfolaurate

Caprylyl Glycol

Caprylhydroxamic Acid

Benzoic Acid

Citric Acid

Sodium Hydroxide

Parfum

Limonene

Water, Sodium C14-16 Olefin Sulfonate, Cocamidopropyl Betaine, Sodium Methyl 2-Sulfolaurate, Sodium Lauryl Sulfoacetate, Sh-Oligopeptide-78, Panthenol, Glycerin, Sodium Phytate, Guar Hydroxypropyltrimonium Chloride, Disodium 2-Sulfolaurate, Caprylyl Glycol, Caprylhydroxamic Acid, Benzoic Acid, Citric Acid, Sodium Hydroxide, Parfum, Limonene

Sodium Cocoyl Isethionate

Disodium Laureth Sulfosuccinate

Glycol Distearate

Sodium Lauroyl Sarcosinate

PPG-5-Ceteth-20

Decyl Glucoside

Coco-Betaine

Divinyldimethicone/Dimethicone Copolymer

Amodimethicone

Polyquaternium-7

Polyquaternium-10

Carbomer

Sodium Benzoate

Sodium Chloride

PEG-55 Propylene Glycol Oleate

Propylene Glycol

Salicylic Acid

Polysorbate 21

Hexyl Cinnamal

Linalool

Trideceth-6

C12-13 Pareth-23

C12-13 Pareth-3

Citral

Geraniol

Glycine

Tocopherol

Cetrimonium Chloride

Phenoxyethanol

Sodium Cocoyl Isethionate, Disodium Laureth Sulfosuccinate, Glycol Distearate, Sodium Lauryl Sulfoacetate, Sodium Lauroyl Sarcosinate, Glycerin, Parfum, PPG-5-Ceteth-20, Decyl Glucoside, Cocamidopropyl Betaine, Coco-Betaine, Divinyldimethicone/Dimethicone Copolymer, Amodimethicone, Citric Acid, Sodium Hydroxide, Polyquaternium-7, Polyquaternium-10, Carbomer, Sodium Benzoate, Sodium Chloride, Limonene, PEG-55 Propylene Glycol Oleate, Propylene Glycol, Salicylic Acid, Benzoic Acid, Polysorbate 21, Hexyl Cinnamal, Linalool, Trideceth-6, C12-13 Pareth-23, C12-13 Pareth-3, Citral, Geraniol, Glycine, Tocopherol, Cetrimonium Chloride, Phenoxyethanol

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Ingredients Explained

These ingredients are found in both products.

Ingredients higher up in an ingredient list are typically present in a larger amount.

Benzoic Acid is an organic acid that shows up in cosmetics as a preservative. It helps keep a product from spoiling by holding back the growth of yeast, mold, and some bacteria.

This ingredient also functions as a fragrance ingredient that helps mask the unpleasant scent of other ingredients.

The way it works is worth understanding; benzoic acid works when the formula is acidic. It is able to sneak into a microbe's cell and mess up how it functions to stop it from growing in an acidic product.

However, the acid switches to an inactive form and stops working if a product isn't acidic enough (above ~5 pH). This is why you'll often see it in low pH products or teamed up with other preservatives to cover the gap.

Safety wise, it's one of the better studied preservatives out there.

The Cosmetic Ingredient Review Expert Panel has concluded this ingredient to be safe for use in cosmetic formulations at concentrations up to 5%.

A large international review found this ingredient had no effects on the human body and had low irritation potential.

Just so you know, real world use is usually much lower than the 5% ceiling (usually 1% of less).

The EU caps it at 2.5% in rinse-off products, 1.7% in oral care, and 0.5% in leave-on products.

One thing worth mentioning (it's nothing to worry about): some people get a little stinging or flushing where they apply it. This isn't a true allergy; it's a temporary and harmless reaction. This is the same kind of mild tingle you might notice from sorbic acid.

Citric Acid is an alpha hydroxy acid (AHA) naturally found in citrus fruits like oranges, lemons, and limes.

Like other AHAs, citric acid can exfoliate skin by breaking down the bonds that hold dead skin cells together. This helps reveal smoother and brighter skin underneath.

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.

Rosacea skin has a lower threshold for acids generally, with 62.5% of rosacea subjects in one study reacting to lactic acid in a sting test. This is why we mark citric acid as a potential rosacea trigger.

However, this ingredient shows up as a pH adjuster or chelator at roughly 0.1-1% in many products. These low levels are unlikely to be an issue for rosacea skin and becomes a potential trigger at exfoliating concentrations (20%). Because everybody's skin is unique, we recommend a patch test if you are unsure.

Cocamidopropyl Betaine is a fatty acid created by mixing similar compounds in coconut oil and dimethylaminopropylamine, a compound with two amino groups.

This ingredient is a surfactant and cleanser. It helps gather the dirt, pollutants, and other impurities in your skin to be washed away. It also helps thicken a product and make the texture more creamy.

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.

Glycerin (or glycerol) is a compound naturally found in your skin. It's a powerhouse humectant that pulls water into the stratum corneum.

Topically, glycerin does several things at once:

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.

Limonene is a fragrance that adds scent and taste to a formulation.

It's found in the peel oil of citrus fruits and other plants such as lavender and eucalyptus. The scent of limonene is generally described as "sweet citrus".

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.

Parfum is a catch-all term for an ingredient or more that is used to give a scent to products.

Also called "fragrance", this ingredient can be a blend of hundreds of chemicals or plant oils. This means every product with "fragrance" or "parfum" in the ingredients list is a different mixture.

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.

Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.

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.

Sodium Lauryl Sulfoacetate is an organic salt with a naturally sweet odor. It is an alternative to traditional sulfates and is commonly found in "sulfate-free" products.

In cosmetics, this ingredient is used to increase the volume of foam, emulsify ingredients, and as a cleansing agent.

As a cleansing agent, sodium lauryl sulfoacetate helps reduce the surface tension of dirt, oil, and other pollutants so they can be rinsed away easily.

Cosmetic Ingredient Review found this ingredient to irritate the eyes and skin in concentrations of 0.18% and 0.7%.

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