(Malin+Goetz) Peppermint Shampoo

Because it has a neutral charge, it is compatible with a wide range of ingredients and stays stable across a broad pH range/water hardiness conditions.

Patch testing has shown it to have the lowest irritation potential among common cleansing surfactants (like SLS).

Typical use levels range from 5-20% in rinse-off cleansers.

One thing worth knowing: The American Contact Dermatitis Society named the parent family, alkyl glucosides, "Allergen of the Year" in 2017. The prevalence of allergy is pretty low but be sure to patch test if you've reacted to "gentle" or sulfate-free cleansers before.

This ingredient is fungal acne safe because the fatty alcohol portion of this ingredient is not within the C11-24 chain length that Malassezia can metabolize.

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.

The "cooling" sensation from mint isn't a real temperature change; menthol actives a nerve receptor in skin that gets triggered by cold. Your brain essentially gets a "cool" signal from it.

Just so you know, allergic contact dermatitis to menthol is documented in literature (but it's kind of uncommon). This is why the percentages allowed in leave-on products are quite low (0.2%). Be sure to patch test if you have sensitive skin.

Though this ingredient is not listed as an EU allergen, it's cousins (Mentha Piperita Oil, menthol and Mentha Viridis Leaf Oil) are.

Due to the high Menthol content of this ingredient, brands are required to label "menthol" as a separate ingredient on the list. The EU regulation labels the allergenic substance, not just the source ingredient, so the menthol carried in this ingredient still has to be declared.

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.

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.

Sodium benzoate works as a preservative by inhibiting the growth of bacteria inside of cells. It prevents the cell from fermenting a type of sugar using an enzyme called phosphofructokinase.

It is the salt of benzoic acid. Foods containing sodium benzoate include soda, salad dressings, condiments, fruit juices, wines, and snack foods.

Studies for using ascorbic acid and sodium benzoate in cosmetics are lacking, especially in skincare routines with multiple steps.

We always recommend speaking with a professional, such as a dermatologist, if you have any concerns.

The dominant fatty acid is lauric acid (44-54%) and then myristic acid (13-19%). There are also small amounts of caprylic, capric, palmitic, oleic, and linoleic acids.

Human testing from CIR has shown no indication this ingredient to be a primary irritant, sensitizer, or phototoxic compound. It's COSMOS-approved for natural and organic products.

Due to the fatty acid content, this ingredient may not be fungal acne safe. Research has confirmed Malassezia can use lauric acid as a food source.

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:

It is able to lift away oil and grime and make a nice lather without stripping your skin, so it's a good pick for sensitive skin.

Safety-wise, it has a good record. The CIR Expert Panel has concluded this ingredient to be safe in cosmetics and concentrations go up to 11% in leave-on products or 13% in rinse-off products.

Despite being derived from coconut oil, this ingredient is fungal acne safe. It's a water-soluble surfactant with no fatty oils or esters left intact on skin for the Malassezia yeast to feed.

Due to the large molecule size, this ingredient is unlikely to penetrate skin.

Both potassium sorbate and sorbic acid can be found in baked goods, cheeses, dried meats, dried fruit, ice cream, pickles, wine, yogurt, and more.

You'll often find this ingredient used with other preservatives.

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.

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.

High percentages of Sodium Lactate can have an exfoliating effect.

Fun fact: Sodium Lactate is produced from fermented sugar.

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.

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.