INCI Guide (II): Ingredient Groups and their Functions

In the first part of this guide, we saw what INCI is, how to interpret it, and why the order matters. Now we're going 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 item does is what allows you to choose with real discernment.

Cosmetic ingredients are grouped by function. These are not rigid categories, as a single ingredient can serve several purposes, but knowing them helps you quickly navigate 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 typically find on the label.

Humectants: attract water to the skin

Humectants are ingredients that draw 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 commonly used humectant in cosmetics due to its effectiveness and low cost. Betaine, derived from beetroot or coconut, hydrates with a very gentle and well-tolerated profile. Beta-glucan acts similarly but with a significant calming bonus for reactive skin.

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

Emollients: soften and improve 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 with a distinct fatty acid profile and a different affinity depending on the skin type. Squalane is another highly valued emollient for its ultra-light texture and compatibility with all skin types, including oily ones.

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

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

Occlusives: seal and protect the barrier

Occlusives form a protective film on the skin that slows down water loss through evaporation. They are always applied on top of humectants and emollients, sealing everything applied 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 at the same time. Vegetable waxes like candelilla wax or carnauba wax serve 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 nutritional contribution. Also, lanolin (Lanolin), of animal origin, was 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 rinse them away. They are the basis 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 strip natural lipids from the skin and scalp, alter pH, and can cause irritation. They are responsible for the feeling of tightness 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 basis 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 account for most of a product's marketing claims, and their effectiveness also varies most 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 renovators

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 skin's surface.

Regulators and uniformizers

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 product.

Tightening and firming agents

They improve firmness and density. Kigelia Africana has recognized tightening properties. Aloe vera soothes, hydrates, 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 in 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 hormone 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 like benzoic acid (Benzoic Acid), potassium sorbate (Potassium Sorbate), or alcohol (Alcohol Denat.) are used in functional concentrations. Solid products, not containing free water, need much less or none, which is another real advantage of solid formats beyond packaging.

Fragrances and allergens: what's 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 trade secrets.

Within that fragrance, there can 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 product without any fragrance 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, they are dispensable ingredients from a functional point of view. Their presence in an INCI is not a cause for alarm, but their absence is not a loss either.

What does not appear in the INCI

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

Reading the INCI with discernment, knowing the categories of ingredients, and having access to reliable information about each one is what makes the back-of-the-label list truly useful. That's also what our ingredient glossary or the Learn More fact sheets are for.