Skin science article
L'Oréal Professionnel Absolut Repair Molecular Repair Leave In Mask Versus REDKEN Acidic Bonding Concentrate 24/7 Night & Day Hair Serum
L'Oréal Professionnel Absolut Repair Molecular Repair Leave In Mask Versus REDKEN Acidic Bonding Concentrate 24/7 Night & Day Hair Serum What's inside Benefits Concerns Ingredients Side-by-side Water Isopropyl Myristate Dimethicone Amodimethicone Triethanolami
L'Oréal Professionnel Absolut Repair Molecular Repair Leave In Mask Versus REDKEN Acidic Bonding Concentrate 24/7 Night & Day Hair Serum
What's inside
Benefits
Concerns
Ingredients Side-by-side
Water
Isopropyl Myristate
Dimethicone
Amodimethicone
Triethanolamine
Phenoxyethanol
Carbomer
Polyquaternium-4
Potato Starch Modified
Hydroxypropyl Guar
Behentrimonium Chloride
Arginine
Trideceth-6
Isopropyl Alcohol
Cetrimonium Chloride
Linalool
Glycine
Serine
Tyrosine
Citric Acid
Glutamic Acid
Coumarin
Benzyl Alcohol
Benzyl Benzoate
Alpha-Isomethyl Ionone
Parfum
Water, Isopropyl Myristate, Dimethicone, Amodimethicone, Triethanolamine, Phenoxyethanol, Carbomer, Polyquaternium-4, Potato Starch Modified, Hydroxypropyl Guar, Behentrimonium Chloride, Arginine, Trideceth-6, Isopropyl Alcohol, Cetrimonium Chloride, Linalool, Glycine, Serine, Tyrosine, Citric Acid, Glutamic Acid, Coumarin, Benzyl Alcohol, Benzyl Benzoate, Alpha-Isomethyl Ionone, Parfum
Squalane
Sodium Polyglutamate
Coco-Betaine
Sodium Chloride
Limonene
Geraniol
Citronellol
Water, Isopropyl Myristate, Dimethicone, Triethanolamine, Amodimethicone, Phenoxyethanol, Squalane, Parfum, Carbomer, Polyquaternium-4, Potato Starch Modified, Hydroxypropyl Guar, Citric Acid, Behentrimonium Chloride, Sodium Polyglutamate, Coco-Betaine, Trideceth-6, Isopropyl Alcohol, Sodium Chloride, Cetrimonium Chloride, Limonene, Linalool, Geraniol, Citronellol, Coumarin, Alpha-Isomethyl Ionone
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Alternatives
Ingredients Explained
These ingredients are found in both products.
Ingredients higher up in an ingredient list are typically present in a larger amount.
Alpha-Isomethyl Ionone is a fragrance. It can be synthetically created or naturally occurring.
The scent of Alpha-Isomethyl Ionone is described as "flowery" but can also be "woody".
Naturally occurring Alpha-Isomethyl Ionone may be found in Saccharomyces cerevisiae, or the yeast used to make wine and bread.
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.
This water-soluble silicone is used for its hydrating and softening properties. It is used to add a silky feel to skincare products and has great benefits for haircare.
In haircare, this ingredient:
Adds shine
Protects color
Offers thermal protection
Boosts hair strength
Does not build up as easily
This ingredient is a preservative and often used for it's anti-static properties. You'll most likely see this ingredient in hair conditioners.
It does not cause irritation or sensitization in leave-on products at 1-5%.
Carbomer is a synthetic thickening and gelling agent. It's basically the ingredient that gives a lot of serums, gels, creams, and sunscreens their smooth, non-sticky texture.
Although legally permitted at very high levels, carbomers are normally used at concentrations below 1%.
It also needs to be neutralized to actually thicken, and because it is a large molecule, it doesn't really penetrate the skin barrier.
Allergy-wise, the risk is very low. Clinical studies show carbomers have low potential for skin irritation/sensitization even at concentrations up to 100%.
A 2024 UK study patch-tested 1,302 patients and found true allergy to the parent group of carbomer to be rare with no confirmed relevant reactions.
This ingredient is a preservative, antimicrobial, and emulsifier. It is often used in cosmetics for its ability to cleanse, condition, and reduce static.
Cetrimonium chloride is a quaternary ammonium salt, meaning it has a water-soluble structure.
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.
Coumarins are a group of substances found naturally in plants. There are over 1300 types of coumarins identified. It has a natural vanilla scent.
Coumarin is an identified EU known allergy, meaning it may cause an allergic reaction when applied to the skin.
In many countries, coumarin is banned as a food additive. However, it can be found in soaps, tobacco products, and some alcohol drinks.
Plants use coumarins as a chemical defense. Some plants that have coumarins include lavender, tonka beans, and yellow clovers.
Dimethicone is a type of synthetic silicone created from natural materials such as quartz. It is also known as polydimethylsiloxane.
What it does:
Dimethicone comes in different viscosities:
Depending on the viscosity, dimethicone has different properties.
Ingredients lists don't always show which type is used, so we recommend reaching out to the brand if you have questions about the viscosity.
This ingredient is unlikely to cause irritation because it does not get absorbed into skin. However, people with silicone allergies should be careful about using this ingredient.
Note: Dimethicone may contribute to pilling. This is because it is not oil or water soluble, so pilling may occur when layered with products. When mixed with heavy oils in a formula, the outcome is also quite greasy.
We don't have a description for Hydroxypropyl Guar yet.
Isopropyl Alcohol is more commonly known as rubbing alcohol. It is most commonly used as a solvent, meaning it helps other ingredients dissolve.
This ingredient is an astringent alcohol. Astringent alcohols may also irritate skin as they high amounts may strip away your skin's natural oils.
Other types of astringent alcohols include:
According to the National Rosacea Society based in the US, you should be mindful of products with these alcohols in the top half of ingredients.
Any type of sanitizing product will have high amounts of alcohol to help kill bacteria and viruses.
Isopropyl Myristate is an ester made by combining isopropyl alcohol with myristic acid.
It is primarily an emollient and penetration enhancer that gives products a lightweight, silky feel without the heaviness of oils.
This ingredient is generally considered non-toxic, non-irritating, and has low absorption potential.
You might have heard that this ingredient clogs pores. This reputation comes from the older rabbit ear studies which are more sensitive than human skin to clogging.
Dermatologist Dr. Zoe Draelos has also confirmed in a peer-reviewed paper that products containing comedogenic ingredients are not necessarily comedogenic themselves.
A small subset of people (~2%) may experience contact sensitivity so patch testing is a reasonable idea if you have reactive skin.
Since this ingredient is an ester of myristic acid (a C14 fatty acid), it falls within the carbon chain range that is known to feed Malassezia. This ingredient may not be fungal acne safe.
Linalool is a fragrance and helps add scent to products. It's derived from common plants such as cinnamon, mint, citrus, and lavender.
Like Limonene, this ingredient oxidizes when exposed to air. Oxidized linalool can cause allergies and skin sensitivity.
This ingredient has a scent that is floral, spicy tropical, and citrus-like.
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.
Phenoxyethanol is one of the most widely used preservatives in skincare (and for good reason!).
It has a large spectrum of antimicrobial activity and especially effective bacteria, yeast, and mold while only having a weak effect on your skin's natural microbiome.
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.
We don't have a description for Polyquaternium-4 yet.
We don't have a description for Potato Starch Modified yet.
We don't have a description for Trideceth-6 yet.
Triethanolamine (TEA) is an emulsifier and pH adjuster. It is created using ethylene oxide and ammonia. This gives Triethanolamine a nitrogen core and a similar scent to ammonia.
As an emulsifier, it prevents ingredients from separating and enhances texture by adding volume to a product.
PH adjusters are common in cosmetic products. The pH of a product can affect the effectiveness of other ingredients. A product with a high pH may also irritate the skin.
If you are looking for the tea leaf ingredient, click here.
Water. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.
So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.
You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!