When you flip a product over and look at the ingredient list, you're looking at the most regulated piece of information on the label. The name, the tagline, the claims on the front ("strengthening," "nourishing," "repair") are marketing, loosely governed and not required to be proven. The ingredient list is different. It's legally mandated in the EU, US, Japan, and Canada, and the rules for how it's written are specific.
The vocabulary looks like another language. Behentrimonium Chloride. Amodimethicone. Butyrospermum Parkii. That's part of why most people skip it. But once you understand the underlying structure, the ingredient list becomes one of the most useful tools in hair care: more reliable than reviews, more honest than product names. It tells you what a product actually is.
The naming system: what INCI means
Every ingredient on a cosmetic label is written using INCI (International Nomenclature of Cosmetic Ingredients), a globally standardized naming system developed in the early 1970s and maintained continuously since. INCI names are nonproprietary: they're not a brand's trade name for an ingredient, but a standardized common name that means the same thing across every label in every country that uses the system.[1]
The system uses different naming conventions depending on ingredient type. Plant-derived ingredients use their Latin botanical name: Butyrospermum Parkii is shea butter; Cocos Nucifera is coconut oil; Aloe Barbadensis is aloe vera. Synthetic and chemical compounds use IUPAC names, the international standard for chemical nomenclature. Water is listed as Aqua. The INCI dictionary, formally called the International Cosmetic Ingredient Dictionary and Handbook, is the reference that governs these names, and its sole purpose is to provide a consistent, consumer-readable identifier for every cosmetic ingredient regardless of brand or country of origin.[2]
The result: ingredients don't change name based on what a company decides to call them. Dimethicone is always dimethicone. Aqua is always water. Understanding this lets you compare products accurately, even across very different brands and price points.
The ordering rule
Ingredients are listed in descending order of concentration, from the highest amount to the lowest.[3] This is the most important structural rule to know.
What it means in practice:
Water (Aqua) is almost always first. Most shampoos, conditioners, and styling products are water-based. Water is typically the largest single component by weight, often making up 60–90% of a formula. If Aqua appears first, you're looking at a water-based product.
Ingredients in positions two through five are doing the heavy lifting. These are present in meaningful concentrations: the primary emulsifiers, cleansers, conditioning agents, and texture-builders that define what a product actually does. A conditioner with Behentrimonium Chloride (a conditioning agent that adsorbs to the hair surface and reduces friction and static) in position three is a deeply conditioning product. The same ingredient appearing in position fifteen is present at a trace amount.
The concentration curve drops fast. Formulas are not evenly distributed across 25 or 30 ingredients. The first five typically account for the majority of the formula by weight. The next five are functional but at lower concentrations. By the time you're at ingredient twelve or fifteen, concentrations are often in the low single-digit percentages, and much lower beyond that.
The one-percent threshold
There is a regulatory rule that changes how the lower portion of the list works. Under EU cosmetics law, the most detailed in the world and used as a global reference standard, ingredients present at one percent or less by weight can be listed in any order after those present above one percent.[4]
In practice, this means: once you reach the preservatives in an ingredient list, you're almost certainly in sub-one-percent territory. Preservatives like phenoxyethanol, sodium benzoate, and potassium sorbate are typically formulated at concentrations below one percent, just enough to prevent microbial growth. By both convention and concentration, they sit at the end of most lists. The cluster of preservatives is a practical landmark: everything listed before it is present at more than one percent, roughly in order of amount. Everything at and after it is present at one percent or less.
This is why "infused with argan oil" on the front of a product can mean very different things. If Argania Spinosa Kernel Oil (argan oil's INCI name) appears after the preservatives, say at position 22, it's present at less than one percent, almost certainly at a fraction of a percent. It's a trace inclusion, not a primary ingredient. It can still appear on the front label because the claim only requires the ingredient to be present, not to be present at any meaningful concentration.
“The first five ingredients account for the majority of any formula by weight. Once you hit the preservatives, everything that follows is likely present at less than one percent.”
Reading by category
Beyond position, it helps to recognize what type of ingredient you're looking at. Most formulas draw from the same broad categories, just in different combinations and proportions.
Solvents: the liquid base that dissolves and carries everything else. Aqua (water) is primary in almost every product. Some formulas use aloe vera juice as a co-solvent.
Surfactants: the cleansing agents in shampoos. The first surfactant listed tells you the primary cleaning strategy of the formula. Sodium Lauryl Sulfate (SLS) is highly efficient but strips aggressively. Sodium Laureth Sulfate (SLES) is gentler. Sodium Cocoyl Isethionate and Decyl Glucoside are among the mildest commonly used options. The sulfates article covers the differences in detail.
Conditioning agents: the core of any conditioner or co-wash. Behentrimonium Chloride and Cetrimonium Chloride are quaternary ammonium compounds that carry a positive electrical charge, which causes them to adsorb (attach to the surface) to negatively charged hair and significantly reduce friction. Amodimethicone is a silicone-based conditioning agent with similar function.
Emollients and occlusives: ingredients that coat the surface or enter the shaft to soften and add slip. Cetyl Alcohol and Cetearyl Alcohol are fatty alcohols. Despite the name, they are conditioning, not drying. Dimethicone is a silicone film-former. Common oils in INCI form: Simmondsia Chinensis (jojoba), Persea Gratissima (avocado), Cocos Nucifera (coconut).
Humectants: ingredients that attract and bind water, both from the formula itself and from surrounding air. Glycerin is the most common. Panthenol (provitamin B5), Propylene Glycol, and Sorbitol are others. Position tells you how concentrated they are: Glycerin at position three is a significantly moisturizing formula. Glycerin at position twelve is a light inclusion.
Proteins: included to strengthen or temporarily reinforce damaged hair. Hydrolyzed Keratin, Hydrolyzed Wheat Protein, Hydrolyzed Silk, and Silk Amino Acids are common. The size of the protein fragment matters: heavily hydrolyzed (broken down into very small fragments) proteins can penetrate the hair shaft; larger protein molecules coat the surface instead. The protein-moisture balance article covers when protein helps versus when it can cause buildup.
Preservatives: the landmark that signals sub-one-percent territory. Phenoxyethanol, Sodium Benzoate, Potassium Sorbate, Benzyl Alcohol. Once you see them, you know the ingredients above were at meaningful concentrations and the ingredients below were trace.
Fragrance: listed as Parfum (EU) or Fragrance (US). A single word that reveals nothing about what scent compounds are present. Under EU regulations, the 26 most common fragrance allergens must be individually named on the label if present above threshold concentrations, so their presence or absence as named ingredients tells you more than the word "Parfum" alone.[5]
What to look for based on your hair
The goal isn't to memorize every INCI name. It's to know which categories matter for your hair and to check where those ingredients land on any given list.
For dry or high-porosity hair: look for humectants (Glycerin, Panthenol, Aloe Barbadensis) in the top five positions, and emollients that appear early enough to be present at meaningful concentrations. A product where Glycerin is third will perform very differently from one where it's twelfth. Your hair needs both moisture attraction and surface sealing, so look for humectants followed by emollients or film-formers.
For fine or low-porosity hair: heavy emollients and butters listed high on a conditioner will likely weigh fine hair down or sit on the cuticle rather than absorb. Look for lighter conditioning agents (Cetrimonium Chloride is lighter than Behentrimonium Chloride) and humectants without dense occlusive layers. Low-porosity hair's cuticle is tight and resists absorption, so ingredient weight and molecular size matter.
For protein-sensitive hair: any Hydrolyzed Protein of any kind listed in the first eight ingredients is present at a significant concentration. If certain products leave your hair feeling stiff, snappy, or brittle (a sign that protein is accumulating without enough moisture to balance it), checking where protein ingredients appear on the list is a useful diagnostic step.
For scalp concerns: in shampoos, look at the surfactant type and position first. For targeted scalp treatments, active ingredients like Zinc Pyrithione (for dandruff), Salicylic Acid (for buildup and flaking), or Piroctone Olamine (antifungal) should appear early enough to be present at functional concentrations.
What ROOTS does with this information
Reading an ingredient list manually is useful. ROOTS' ingredient analysis does it systematically across the full list, evaluating what's present, where it appears, what category it belongs to, and how that combination of ingredients maps to your specific hair profile across multiple dimensions at once.
When you take the ROOTS quiz, the matched products you receive are based on this kind of ingredient-level reading applied at scale. You're not getting products filtered by "has argan oil" or "sulfate-free." You're getting products matched to what your porosity, texture, and scalp type actually need, based on what formulas genuinely contain and in what quantity.
Understanding the list yourself is useful even independently of that. It's how you stop being misled by front-of-pack claims and start reading what's actually in the bottle.