Deconstruct Nourishing Conditioner

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.

It has a very saturated profile (stearic acid ~34 to 36%, oleic acid ~30 to 40%, and palmitic acid ~24 to 29%) that makes it a strong occlusive: it sits on top and slows water escaping from skin.

Concentration data shows that it can show up anywhere from a few percent in lotions up to 100% in balms, and the FDA lists cocoa butter as an OTC skin protectant active at 50-100%.

The CIR has reviewed it and concluded it to be safe as used in cosmetics.

This is one of the ingredients with a comedogenic score of 4/5 from the rabbit ear test. Just know that a later human study did find that finished products containing high-comedogenic ingredients like cocoa butter did not increase microcomedone formation.

The fair call here is that this ingredient is most likely fine on body or low-percentage formulas, but can potentially be riskier as a heavy leave-on facial product if you break out easily.

Cocoa butter may not be fungal acne safe; it is a triglyceride of C16-18 fatty acids that the Malassezia yeast can metabolize.

Allergies to cocoa butter are rare and uncommon, but a few cases have been documented (mostly in cases where the person ate chocolate). So if you have a tree nut allergy, be sure to patch test or avoid.

In vitro research found an increase in skin hydration by 58% and a decrease in TEWL by 37.8% after 24 hours of applying this ingredient (pretty impressive for a single ingredient!).

Besides hydration, shea butter also contains triterpenes that have anti-inflammatory potential. In particule, lupeol cinnamate has shown the highest anti-inflammatory activity in vivo.

Shea butter also contains vitamins A and E which may contribute to antioxidant activity.

While Shea Butter has an SPF rating of about 3-4, it is not a sunscreen replacement.

This ingredient may not be fungal acne safe because its fatty acids fall within the C11-C24 range that the Malassezia yeast can metabolize.

This ingredient shows up on a lot of "pore-clogging" lists but there's no real evidence behind that. It doesn't even have a comedogenic rating from an actual study; the numbers you'll find online come from blogs citing other blogs.

Ratings for other ingredients mostly come from a 1980s rabbit ear test. This test doesn't translate well to human skin or to real products because the ingredient sits at a much lower percentage.

Some people still find it breaks them out. So if that's you, definitely trust your skin. Just know this one's based on experience and not evidence.

Concentration-wise, safety review reports the wider trimonium family shows up between 0.0005% to 10% in rinse-off products and 0.001% to 4% in leave-on products.

This ingredient is commonly used at ~1–5% when acting as the emulsifier.

Allergies to this ingredient are rare; the CIR panel noted the literature lacks clinical reports of irritation or sensitization and patch tests on finished products containing it came back clean.

Though it has "alcohol" in the name, it is not related to denatured alcohol or ethyl alcohol.

The FDA allows products labeled "alcohol-free" to have fatty alcohols.

This ingredient may not be fungal acne safe. It is a primary fatty alcohol with a chain length above 12 carbons. A study from 2019 show Malassezia can feed on fatty alcohols in this range, so it may trigger fungal acne in those prone to it.

As a humectant, hydrolyzed keratin helps draw moisture from the air to your hair and skin. This helps keep your skin and hair hydrated.

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.

Those are medium-chain fats which is why it melts fast on skin and feels lighter than stearic-heavy butters like shea or cacao.

In skincare, this butter works as an emollient and a temporary occlusive that helps soften the skin's surface and slows water loss.

Just to be upfront: there's no published human clinical trials on this ingredient and everything known about how it behaves on skin is from the fatty acid composition + general body of data on refined plant oils. At this time, marketing claims about wrinkles, elasticity, or "deep repair" are unsupported.

Industry survey data shows concentrations between 0.001%-7% for leave-on products and rinse-off products are capped around 0.2%.

No one has tested murumuru butter for comedogenicity in humans; the comedogenic ratings floating around trace back to lauric and myristic acid scores from the 1984 rabbit ear assay.

The author of that study later said that testing on rabbit ears is not ideal and human testing found that comedogenic ratings cannot predict how a finished formula will behave. It all comes down to formula, concentration, and your skin.

Malassezia is lipid dependent and feeds on free fatty acids between C11-24 chain lengths. This ingredient is made up entirely of chains in that range, so it may not be fungal acne safe.

This ingredient is often chosen as a biodegradable, gentler-sounding alternative to EDTA. It also pulls double duty as a mild humectant and pH buffer.

Typical use levels sit around 0.1-1% and supplier documents list up to 10% as an acceptable ceiling. Industry data found this ingredient family is mostly used well below 1% in leave on products.

Allergy risk is very low; animal testing has found it to be non-irritating to skin and eyes, mutagenicity assays came back negative, and there are no published reports of allergic contact dermatitis to it.

As a preservative, it is used to stabilize products and prevent them from degrading. Specifically, BHT prevents degradation from oxidation.

The concerns related to BHT come from oral studies; this ingredient is currently allowed for use by both the FDA and EU.

However, it was recently restricted for use in the UK as of April 2024.

More research is needed on applying biotin topically. However, taking biotin orally has been shown to help nourish the skin, hair, and nails. They play a role in forming skin-hydrating fatty acids.

Biotin is water-soluble. It can be found in foods such as fish, eggs, dairy, nuts, and meat. Vitamin H stands for "haar" and "haut". These are the German words for hair and skin.

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