Guide to Cosmetic Ingredients: The Science of Functional Skincare

How many times have you read the label on a serum or face cream and wondered whether all those promises would turn into real results? In the vast world of cosmetics, a new miracle ingredient is touted every day, fueled by viral trends, only to be promptly forgotten. The race for the latest product never ends, and your skin suffers — not to mention your wallet.

Skin health isn't built by chasing the latest trends, but by relying on smart, functional formulations tailored to your skin type and suited to the stage of life you're going through: during menopause, your needs differ from those you have when you notice your first fine lines at 30.

Your skin needs to be accommodated, listened to, and protected. In this guide, we'll explore the world of functional ingredients: not a list of complex names, but a path to understanding what really works, how active ingredients act on the structure of the skin, and how to choose the right combination without stressing it.

If you're starting from scratch, before looking at active ingredients, it's worth getting the bigger picture: what it really means to care for your skin, which steps you need, and in what order. We covered this in our article on skincare: what it means and where to start.

[INDICE:h2]

What are functional ingredients?

Every cosmetic product is made up of a base, or excipient, which determines its texture, and a series of active substances. Functional ingredients are biologically active molecules included to perform a targeted action: stimulate collagen, neutralize free radicals, restore hydration, like hyaluronic acid, or soothe inflammation, like aloe vera. These are joined by substances that stabilize and preserve the formula: they do not act directly on the skin, but they are what allows the product to work right through to the last application.

The presence of an ingredient on the label (INCI) is not enough to guarantee its effectiveness. The real difference lies in the concentration, the stability of the formula, and the finished cosmetic’s ability to deliver the active ingredient where it is needed. A good rule of thumb: if a brand is proud of the percentage of an active ingredient, it states it. If it doesn’t, there’s often a reason.

This is the same criterion that distinguishes a truly functional product from one that merely claims to be. The term cosmeceutical arose precisely from this need, and whoever coined it attached three specific conditions to it — penetration, a known mechanism of action, and clinical studies on humans. No authority verifies them: these are questions buyers need to ask.

If it’s true that dermatology’s cornerstones remain a reliable compass, it’s equally true that new developments exist for a reason: research moves forward. Consider vitamin C: in its pure form, it is formidable but extremely fragile. L’innovation has made it possible to formulate advanced solutions such as stabilized vitamin C (Et-VC), the form chosen by LeLang for its serums, which can resist oxidation and provide a prolonged brightening effect without irritating the epidermis.

We should also make a case for what we might call natural science. There is a common misconception that the natural world and the laboratory are at odds. Quite the opposite: the best botanical extracts are studied, purified, and standardized in the lab precisely so they can become reliable, reproducible active ingredients.

The main types of functional ingredients

Not all active ingredients work the same way: some help the skin attract water, others help it retain it, while others promote surface renewal, soothe sensitivity, or protect against oxidative stress.

• Humectants — such as hyaluronic acid, glycerin, urea, and amino acids in the natural moisturizing factor: they draw water into the outermost layers and help keep skin supple.
• Hydrating and replenishing ingredients — ceramides, biomimetic lipids, and emollients strengthen the skin barrier and reduce transepidermal water loss (TEWL).
• Exfoliants — work on cell turnover and improve uneven texture, dullness, enlarged pores, and marks left by blemishes, provided they're included in well-balanced formulas.
• Purifying and absorbing ingredients — like green clay, which works by adsorbing excess sebum: these are the oldest active ingredients in the skincare repertoire and are still effective, as long as you don't use them too often.
• Calming and soothing ingredients — valuable when skin feels tight, reddens easily, or reacts to environmental changes.
• Antioxidants — fight free radicals generated by UV rays, pollution, and external aggressors.
• Revitalizing and renewing ingredients — support firmness, radiance, and overall skin quality.

A well-designed formula combines different categories that work synergistically to address a real need.

The antioxidant shields: vitamin C and ferulic acid

Pollution, UV rays, and urban stress trigger the production of free radicals, among the main causes of premature skin aging and so-called cortisol face. Vitamin C is one of the most studied active ingredients for its anti-aging and skin-evening properties.

Its weakness is instability. This is where ferulic acid comes in: studies conducted at Duke University by Sheldon R. Pinnell's research group have shown that adding it stabilizes vitamins C and E and doubles the formula's photoprotection. Working in synergy, these ingredients neutralize damage before it affects collagen.

A well-designed antioxidant system never relies on a single molecule, because each covers different ground: vitamin E protects membrane lipids, which vitamin C cannot reach, while resveratrol also works by slowing the degradation of existing support fibers.

This is the principle behind the formulation of Ferulic + HA Serum.

Hydration and barrier repair

As we saw in the guide to the skin barrier, this structure is largely made up of ceramides. The most effective ingredients for strengthening it are those that are compatible with our biology: hyaluronic acid, which draws in water molecules to plump the tissues, and urea, which keeps the skin soft and elastic.

Cell renewal: retinoids and brightening ingredients

For fine lines, enlarged pores, and acne marks, vitamin A derivatives known as retinoids receive near-unanimous support from specialists: retinol stimulates cell turnover and supports regeneration.

Alongside retinoids, signal peptides work with much greater tolerability: Matrixyl is the most studied in its category and works by stimulating collagen production instead of accelerating cell turnover.

For discoloration and hyperpigmentation, vitamin C is complemented by ingredients such as lycopene, which protects against sun-induced oxidative stress, and azelaic acid, which acts on the enzyme involved in melanin production, working selectively on overactive cells.

Daily protection: the only real anti-aging step

If there's one point on which the scientific community won't compromise, it's sun protection. UV filters do more than prevent sunburn: they're true anti-aging shields. Without daily protection, even the most expensive serum loses much of its effectiveness because it's working to repair damage that continues to accumulate.

If you've ever wondered what the real difference is between the two main types of filters, we discuss it in our guide to chemical and physical sunscreens.

Beyond classic ingredients: neurocosmetics

The skin is not just a covering, but an extension of the nervous system. Active ingredients like niacinamide and peptides, together with specifically neurocosmetic ingredients, act on the signals that travel through the skin, helping it regain balance.

The LeLang philosophy

We believe quality matters far more than quantity. You don’t need ten complicated steps, but stable, well-balanced formulas backed by evidence. Skin health is a journey that calls for consistency and respect for your own pace: stop fighting your skin and start listening to it.

You can also find LeLang products at our partner pharmacies across the country.

Sources for this article

• Studies on the stabilization of vitamins C and E by ferulic acid and the doubling of skin photoprotection, Journal of Investigative Dermatology, vol. 125, no. 4, 2005, by Sheldon R. Pinnell's research group at Duke University.
• Regulation (EC) No. 1223/2009 on cosmetic products, for the designation of ingredients on the label (INCI).

On the website: vitamin C · vitamin E · resveratrol · ferulic acid · azelaic acid · green clay · amino acids in cosmetics · chemical and physical sunscreens · what is cosmeceuticals