Ingredients · Beginner ·
What does each ingredient do? EU functions explained
Every cosmetic ingredient is filed under a job. Here are the standard functions from the EU ingredient list, in plain language, with examples you can find in the library.
Key takeaways
- The EU gives each cosmetic ingredient one or more official functions, such as humectant, emulsifying agent or preservative.
- Most formulas are built from just five jobs: a base (solvent), moisturisers, structure, a preservation system and a few actives or colourants.
- One ingredient often has several functions: cetyl alcohol is an emollient, a thickener and an emulsion stabiliser at once.
- Some functions (hair dyes, depilatories, oxidizing and reducing agents, bleaching agents) are heavily regulated and are not beginner territory.
When the European Union listed every cosmetic ingredient, it gave each one a function: the job it usually does in a product. The original list was prepared with the European cosmetics industry association, and the same functions are still used today in the Commission's ingredient database, CosIng. Learning them is a quick way to read any ingredient list: you stop seeing 40 strange names and start seeing a handful of jobs.
The big picture: five jobs in almost every formula
| Job | Functions involved | Example in a lotion |
|---|---|---|
| The base | Solvents | Water (Aqua) |
| Comfort and moisture | Humectants, emollients | Glycerin, jojoba oil |
| Structure and texture | Emulsifying agents, emulsion stabilisers, viscosity controlling agents, film formers | Emulsifier, cetyl alcohol, xanthan gum |
| Keeping it safe and stable | Preservatives, antioxidants, chelating agents, buffering agents | Preservative, tocopherol, Disodium EDTA, citric acid |
| The extras | Botanicals, biological additives, colorants, UV absorbers, other additives | A plant extract, an iron oxide, a UV filter |
1. The base and the moisture
Solvents
Substances that dissolve other ingredients. Water is the main one, but glycols such as propanediol and butylene glycol, and alcohol, also act as solvents. A solvent decides where an ingredient can live: water-soluble ingredients need a water-based solvent, oil-soluble ones need an oil.
Humectants
Substances that hold and retain moisture. Glycerin, sodium PCA, sorbitol and sodium hyaluronate pull water into the product and the upper skin layer. Too much can feel sticky, and in very dry air humectants can draw water out of the skin instead. See humectants, emollients and occlusives.
Emollients
Substances that soften and smooth the skin. Plant oils, butters and esters such as caprylic/capric triglyceride fill the gaps between skin cells and make skin feel supple. They also decide the feel of the product: light and dry, or rich and cushiony.
2. Structure and texture
Emulsifying agents
Surface-active ingredients that let oil and water mix into a stable emulsion. Their strength is described by the HLB number, and you can work out the right mix with the HLB calculator. Read more in emulsions explained.
Emulsion stabilisers
Ingredients that help emulsification and extend shelf life without being the main emulsifier. Fatty alcohols such as cetyl and cetearyl alcohol are the classic example: they add body and keep droplets from merging.
Viscosity controlling agents
Substances that raise or lower thickness. Gums (xanthan), carbomer, cellulose derivatives and waxes thicken; some solvents and salts can thin or thicken depending on the system. Choosing one is covered in thickeners and stable emulsions.
Binders
Ingredients that hold solid mixtures together, such as pressed powders and solid bars. Clays, starches and some waxes do this job.
Film formers
Ingredients that leave a continuous thin film on skin, hair or nails when the product dries. Examples are pullulan and polyquaternium polymers. They give hold in hair styling, smoothness in face masks and long wear in colour products.
Opacifiers
Substances that make a clear or see-through product cloudy or opaque. They are used for creamy white looks in shampoos and for coverage. Titanium dioxide and zinc oxide also do this, in addition to their UV role.
3. Cleansing and physical action
Surfactants
Substances that lower surface tension so that oil and dirt can be washed away and the product spreads evenly. They are the backbone of cleansers, for example sodium cocoyl glutamate and coco-glucoside. Emulsifiers are surface-active too, which is why the two functions overlap.
Abrasives
Substances that rub away material from the skin surface, or polish teeth. Jojoba beads, silica and sodium bicarbonate are examples. Microplastic beads are restricted in the EU, so choose biodegradable particles.
Absorbents
Substances that take up water or oil. Kaolin and other clays, starches and silica soak up excess sebum in masks and powders.
Antifoaming agents
Substances that reduce foam, either during manufacturing or in the finished product. Dimethicone is a common one. At home, foam from a surfactant mixture can trap air and make dosing difficult: stirring slowly is the easy fix.
4. Keeping a product safe and stable
Preservatives
Substances whose main purpose is to stop microorganisms growing in the product. Any formula with water needs one. See preservatives 101. Allowed preservatives and their maximum levels are fixed by law.
Antimicrobials
Substances that reduce the activity of microorganisms on the skin or body, rather than in the jar. Think of the active ingredients in a deodorant or an acne product. The difference matters: a preservative protects the product, an antimicrobial acts on you, and some ingredients can do both.
Antioxidants
Substances that stop oxidation and rancidity, mainly in oils and butters. Tocopherol (vitamin E), ascorbyl palmitate and rosemary extract are common. They do not protect against microbes. Many skincare actives are antioxidants too, but their job on the skin is different from the job in the jar.
Chelating agents
Substances that grab metal ions (from hard water, clays or equipment) which would otherwise make a product discolour, go rancid or weaken the preservative. Disodium EDTA, sodium phytate, sodium gluconate and tetrasodium glutamate diacetate are examples. A small amount, often 0.05-0.2%, makes a big difference.
Buffering agents
Substances that adjust and hold the pH. A pair such as citric acid with sodium citrate, or lactic acid with sodium lactate, resists pH drift. See why pH matters.
Anticorrosives
Substances that protect the packaging from corrosion. They matter mostly for metal containers and aerosol cans, and you will rarely add one in a small-batch formula.
5. Sun protection
UV absorbers
Substances that filter UV rays to protect the skin, or to protect the product from sunlight. Only UV filters on the approved list may be used for sun protection, each with its own maximum concentration. A homemade SPF cannot be shown to protect without lab testing, so treat sunscreen as an advanced project. See selling your formulas.
6. Colour, smell and the feel on the skin
Cosmetic colorants
Substances that colour the product or the skin. Only colourants on the approved list are allowed, and they appear as CI numbers on the label (for example CI 77491 for red iron oxide).
Deodorant agents
Substances that reduce or mask unpleasant body odour. This covers odour absorbers and antibacterial helpers.
Antiperspirant agents
Substances that reduce sweating, usually aluminium salts. Reducing sweat is a different job from deodorising, and the two are regulated differently.
Antistatic agents
Substances that reduce static electricity, which makes hair fly away. Cationic ingredients such as behentrimonium chloride cling to the negative charge of hair and are the usual choice in conditioners.
7. Special-purpose functions (handle with care)
These functions involve strong chemistry. Some are restricted to professional use, many need a safety assessment and specific warnings, and none belongs in a first batch.
| Function | What it does | Why take care |
|---|---|---|
| Antidandruff agents | Control dandruff in hair products | Each has a legal maximum; examples include zinc pyrithione, piroctone olamine and climbazole |
| Bleaching agents | Lighten hair or skin | Strong oxidisers or restricted skin-lightening actives; limits and warnings apply |
| Hair dyes | Colour hair | Strongly regulated; allergy (patch) testing is advised, and many dyes are banned |
| Depilatory agents | Dissolve unwanted body hair | Alkaline and irritating; thioglycolates can burn if left too long |
| Oxidizing agents | Add oxygen to change another substance | Used in dyes and perms, for example hydrogen peroxide; can burn skin and eyes |
| Reducing agents | Remove oxygen or add hydrogen | Used in perms and relaxers; strong smell and irritant |
| Denaturants | Make alcohol unpalatable | Alcohol in cosmetics is denatured so that it cannot be drunk |
| Oral care agents | Care for the mouth (toothpaste, mouthwash) | Fluoride and others have specific limits and warnings |
| Propellants | Gas that pushes a product out of an aerosol can | Flammable gases under pressure; this is industrial territory |
8. The catch-all functions
Botanicals
Substances derived from plants, mostly by physical means such as pressing, infusion or steam distillation: extracts, waters and essential oils. Strength and quality differ between suppliers, and they can contain allergens.
Biological additives
Substances of biological origin added for a specific feature: proteins, enzymes, peptides, ferments and similar.
Additives
A catch-all for substances added, often in small amounts, to improve a desirable property or suppress an undesirable one when no other category fits.
How to use this when you formulate
- Check that every job is covered. A water-based lotion without a preservative, or an oil without an antioxidant, has a gap.
- Do not double up for no reason. Three thickeners and two emulsifiers is not twice as good.
- Look at a product label. Write the function next to each INCI name to see how the formula is built. How to read an INCI list shows how.
- Use the library. Every ingredient in the ingredient library shows its function, usage range and handling notes.