INCI Guide (II): Ingredient Groups and their Functions

In the first part of this guide, we learned what INCI is, how to interpret it, and why the order matters. Now, let's go a step further: understanding the function of each ingredient according to its category. Because knowing how to read a list is useful, but knowing what each ingredient does is what allows you to choose with real discernment.

Cosmetic ingredients are grouped by function. These are not rigid categories; the same ingredient can fulfill several functions at once, but knowing them allows for quick orientation when looking at any INCI list.

Below, we review the main groups with some representative examples of each. This is a practical guide to identify them, know what to look for, and what you will commonly find on the label.

Humectants: attract water to the skin

Humectants are ingredients that capture water from the environment or from the deeper layers of the skin and retain it in the superficial layers. Their effect is immediate and visible: the skin becomes hydrated, looking smoother and plumper.

The most well-known is hyaluronic acid, capable of retaining up to a thousand times its weight in water. Glycerin, present in almost any cream or serum, is the most widely used humectant in cosmetics due to its effectiveness and low cost. Betaine, obtained from beetroot or coconut, moisturizes with a very gentle and well-tolerated profile. Beta-glucan acts similarly but with an added soothing benefit relevant for reactive skin.

In the INCI, you will recognize them as: Sodium Hyaluronate, Glycerin, Betaine, Beta-Glucan.

Emollients: soften and provide flexibility

Emollients fill the spaces between skin cells, smoothing the surface and improving flexibility and feel. They are responsible for that silky skin sensation after applying a product.

Vegetable oils are emollients par excellence: argan, jojoba, avocado, baobab, coconut. Each has a distinct fatty acid profile and a different affinity depending on the skin type. Squalane is another highly valued emollient for its ultralight texture and compatibility with all skin types, including oily ones.

In conventional cosmetics, silicones often fulfill this role: Dimethicone, Cyclopentasiloxane, Cyclohexasiloxane. They provide an immediate, very pleasant sensation but form an impermeable layer on the skin without providing real nourishment.

In the INCI, vegetable oils appear with their botanical Latin name: Argania Spinosa Kernel Oil, Simmondsia Chinensis Seed Oil, Persea Gratissima Oil.

Occlusives: seal and protect the barrier

Occlusives form a protective film over the skin that slows down water loss by evaporation. They are always applied after humectants and emollients, sealing everything underneath. They are especially useful for very dry skin, in cold climates, or as part of the nighttime routine.

Shea butter is the most versatile natural occlusive: it nourishes, protects, and soothes simultaneously. Vegetable waxes like candelilla wax or carnauba wax perform a similar function and frequently appear in lip balms and solid products.

In conventional cosmetics, the occlusive par excellence is petroleum jelly (Petrolatum), derived from petroleum: very effective at sealing but without any nutritive contribution. Lanolin (Lanolin), of animal origin, was also widely used before the expansion of plant-based alternatives.

Surfactants: cleanse and emulsify

Surfactants are ingredients with a molecular structure that allows them to act between water and oil, capturing dirt and sebum so that water can wash them away during rinsing. They are the base of any cleansing product.

But not all surfactants are the same. Sulfates, such as Sodium Lauryl Sulfate (SLS) or Sodium Laureth Sulfate (SLES), cleanse effectively but are aggressive: they excessively remove the skin's and scalp's natural lipids, alter pH, and can cause irritation. They are responsible for the tight feeling after washing.

Coconut-derived surfactants are the most common alternative in natural cosmetics: Sodium Cocoyl Isethionate (SCI), Coco-Glucoside, Sodium Cocoamphoacetate. They cleanse while respecting the skin barrier, with adjusted pH and without drying it out. They are the base of syndets and sulfate-free shampoos.

Surfactants also act as emulsifiers: they allow water and oils to coexist in a cream without separating. Without them, lotions and creams as we know them would not exist.

Actives: ingredients with specific cosmetic functions

Actives are ingredients with a specific biological action on the skin: they stimulate, renew, brighten, strengthen. They are what justify most of a product's marketing claims, and also what varies most in efficacy depending on their concentration and the quality of the formula.

Some of the most relevant and well-documented:

Antioxidants

They protect the skin from oxidative damage caused by pollution, sun, and stress. Vitamin C, astaxanthin, green tea, and pomegranate are examples with a solid scientific basis.

Cell renewers

They stimulate skin renewal, improve texture, and reduce wrinkles. Bakuchiol and phytoretinol are plant-based alternatives to retinol, with much better tolerance profiles. PHAs and succinic acid gently and controllably renew the surface.

Regulators and uniformity agents

They act on sebum, tone, and the skin barrier. Niacinamide is the most versatile of all: it regulates, unifies, strengthens, and soothes. Combined with N-Acetyl Glucosamine, it complements its action on blemishes and uneven tone. Our niacinamide serum is an example of this synergy between effective active ingredients that enhance their effects in a minimalist and well-formulated formula.

Firming and tightening agents

They improve firmness and density. Kigelia africana has recognized tightening properties. Aloe vera soothes, moisturizes, and helps maintain elasticity.

Preservatives: necessary, but not all are equal

Every cosmetic product that contains water needs preservatives. Without them, the product would be contaminated with bacteria and fungi within days. Preservatives are not the enemy; they are a technical necessity.

The problem is not their presence, but which ones are used. Parabens (Methylparaben, Propylparaben, Butylparaben) were the industry standard for decades. They are effective and stable, but their association with hormonal disruption has brought them under scrutiny, especially in high concentrations or with continuous use. Many brands have removed them, although the scientific debate remains open.

Phenoxyethanol (Phenoxyethanol) is the most common substitute in conventional cosmetics and also in many natural products. In correct concentrations, it is safe, but in excess, it can irritate very sensitive skin.

In well-formulated natural cosmetics, preservatives such as benzoic acid (Benzoic Acid), potassium sorbate (Potassium Sorbate), or alcohol (Alcohol Denat.) are used in functional concentrations. Solid products, as they do not contain free water, need much less or no preservatives, which is another real advantage of solid formats beyond packaging.

Fragrances and allergens: what lies behind "Parfum"

The word Parfum or Fragrance in an INCI list is one of the most opaque terms. It can hide dozens of different ingredients under a single name because fragrance formulas are protected as industrial secrets.

Within that fragrance, there may be components that cause reactions in some skin types: fragrance allergens. European regulations require declaring the most common ones when they exceed certain concentrations: Limonene, Linalool, Citral, Geraniol, Eugenol, Cinnamal, among others. Some come from natural essential oils, others are synthetic. Their presence does not mean the product is bad, but it is relevant information for those with reactive skin or a history of allergies.

In conventional cosmetics, artificial fragrances are especially common and complex in composition. In cleaner formulations, individually declared essential oils are used, allowing consumers to know exactly what they are exposed to.

A fragrance-free product will appear in the INCI without any mention of Parfum, Fragrance, or essential oils. This is the safest option for very sensitive or reactive skin.

Colorants: when color adds nothing

Cosmetic colorants have no function for the skin. They are there to make the product visually appealing, nothing more. In the INCI, they appear with CI codes followed by a number: CI 77491 (red iron oxide), CI 42090 (blue), CI 19140 (tartrazine yellow).

Some synthetic colorants have generated controversy due to their potential irritant or allergenic properties. In natural cosmetics, mineral or plant-based pigments are used, but in any case, these are dispensable ingredients from a functional standpoint. Their presence in an INCI is not an alarm signal, but their absence is not a loss either.

What does not appear in the INCI

It is worth remembering, as we already pointed out in Part I, that INCI has its limits. It does not indicate exact concentrations, it does not distinguish between a virgin cold-pressed oil and a refined one, and it does not guarantee the real effectiveness of a product. It is a transparency tool, not a quality certificate.

Reading the INCI with discernment, knowing the ingredient categories, and having access to reliable information about each one is what makes the list on the back label truly useful. For this purpose, we also have our ingredient glossary or the Learn More information sheets.