Cosmetics: chemistry you can feel on your skin

Long before we knew what a polymer or a surfactant was, there were already people who had mastered the art of transforming natural ingredients into beauty treatments. Cleopatra, for example, did not need a laboratory to create her legendary donkey milk baths, oil blends and clay masks. But, even without knowing it, she was applying basic principles of chemistry: emulsions, natural acids, minerals with astringent properties.

Lactic acid, found in milk, for example, belongs to the alpha hydroxy acid (AHA) family, known today for its exfoliating and cell renewal effects. Clay masks exploit the adsorption of impurities (no, that's not a mistake – adsorption is the process by which molecules or ions from a fluid are attracted to or retained on a solid surface) and the drying effect provided by minerals such as kaolin or bentonite.

The ancient Egyptians used charcoal and crushed minerals to make “kajal” (a kind of primitive eyeliner); the Romans mixed wine and barley flour for face masks; and Eastern civilisations exploited roots, flowers and spices to care for their skin and hair.

In these preparations, phenolic compounds, terpenes, tannins and natural alkaloids already performed antioxidant, anti-inflammatory or aromatic functions.

The history of cosmetics is, after all, a history of chemistry, albeit intuitive. The alchemy of beauty began in temples and palaces, but evolved into laboratories, factories and research centres, where science became the great ally of aesthetics.

When beauty began to “speak chemistry”

It was in the 20th century that cosmetics ceased to be just a traditional or homemade ritual and became an industry with rules, standards and, above all, research. Major brands began to invest in laboratories and teams of chemists to create effective, safe, consistent and easily reproducible products.

With the synthesis of new molecules and the development of emulsifiers, preservatives and artificial fragrances, modern cosmetics gained a scientific language. Ingredients such as hyaluronic acid (a high molecular weight polysaccharide capable of retaining up to a thousand times its weight in water, thus providing deep hydration), retinol (vitamin A1, which stimulates collagen production and accelerates cell renewal) and UV filters (such as avobenzone or titanium dioxide, which work by absorbing or reflecting ultraviolet radiation, protecting cellular DNA) were born from accumulated chemical knowledge and revolutionised skin care.

It was also at this time, with the impetus of new developments, that regulations began to emerge to ensure product safety. Chemistry now has a dual role: to create and to protect.

Beauty with science and conscience

Nowadays, talking about cosmetics means talking about high technology – but also about responsibility. Innovative formulas include microcapsules that release ingredients throughout the day, adaptive textures that react to skin temperature, and peptides with specific action on wrinkles and firmness. But the chemistry of cosmetics is not just about effectiveness. Safety is one of the pillars of development: each ingredient is tested and evaluated at various stages before reaching the market, in accordance with strict standards imposed by bodies such as the European Commission and the FDA (in the US). This is “safety chemistry” in action.

This involves tests such as dermal toxicity assessment, physical-chemical stability, skin compatibility, phototoxicity studies and rigorous microbiological control.

Alongside technological innovation and safety, there is also growing concern for sustainability. Solid cosmetics (such as shampoo, cream and deodorant bars), biodegradable formulas and recyclable packaging are transforming the sector. And, once again, all this is possible thanks to chemical research, which seeks new ways to care for the skin without harming the planet.

Biopolymers derived from algae or cellulose, plant-based surfactants and green solvents (such as bio-based ethanol) are some of the chemical solutions that reduce environmental impact.

Many of these solutions are the result of so-called bio-inspiration: formulas that seek to mimic or adapt natural processes, with ingredients extracted from algae, mushrooms, medicinal plants and even marine bacteria. Proof that “natural” and “chemical” are not opposing concepts. After all, everything that exists is made of atoms and molecules.

The chemistry of yesterday, today and tomorrow

If Cleopatra were alive today, she would have more than milk and essential oils at her disposal – she could choose between serums with ferulic acid, creams with probiotics or masks with nanoparticles. But ultimately, the logic is the same: to use available resources to improve appearance, comfort and self-esteem.

Cosmetics are one of the most sensory expressions of chemistry in our daily lives. They are in the silky texture of a cream, the fragrant foam of a shower gel, the vibrant colour of a lipstick. It is a science that can be felt on the skin.

And it will continue to evolve, with greater precision, more personalisation and greater sustainability. Beauty has always been chemistry – only the packaging has changed.