What is the composition of a moisturising cream?

The use of cosmetics dates back several millennia. The earliest documented evidence appears around 6,000 years ago in Ancient Egypt, where ingredients such as aloe vera were already used to protect the skin, make it more supple, and reduce the signs of ageing. The Egyptians also employed scented oils and ointments to cleanse the skin, mask body odours, and shield themselves from the intense sun and the desert’s dry winds. These practices were later passed on to the Greek and Roman civilisations, laying the foundations for the skincare routines we know today.

Behind the composition of a moisturising cream lies, in fact, a complex formulation designed to protect the skin, maintain its hydration and improve its appearance over time.

A moisturising cream: first and foremost a structured emulsion.

From a physico-chemical standpoint, the vast majority of moisturising creams are emulsions, that is to say of stable mixtures of two phases that are normally immiscible : an aqueous phase and an oily phase. This arrangement enables the simultaneous delivery to the skin of hydrophilic and lipophilic substances, thereby supporting both hydration of the stratum corneum and the restoration of the hydrolipidic film. Several types of emulsions can be distinguished. Oil-in-water (O/W) emulsions, also known as direct emulsions, are the most common in cosmetics because they leave a light finish without a pronounced greasy film and favour relatively rapid diffusion of active ingredients into the skin. Conversely, water-in-oil (W/O) emulsions, or indirect emulsions, deposit a more persistent lipid layer, sought after in richer treatments, particularly used at the night or for very dry skin.

After application, the water within the cream gradually evaporates, leaving a film composed of lipids, humectants and other non-volatile compounds on the skin surface. This film helps make the skin more supple, more hydrated and to reinforce its barrier function.

Excipients, essential yet often little-known.

Beyond its emulsion structure, a moisturising cream relies on a set of excipients essential for its long-term stability and good skin tolerance. These substances, mostly devoid of biological activity, nevertheless perform essential roles. Some enable the homogeneous blending of the aqueous and oily phases, others maintain viscosity, while others prevent microbial contamination, adjust the pH or protect sensitive ingredients from oxidation.

A stable formulation requires several categories of complementary agents, including emulsifiers, thickeners and preservatives, solvents and pH regulators.

Their nature, concentration and interactions directly govern the product’s texture, ease of application and shelf life. The aqueous phase, predominant in many creams, forms the base of the formulation and serves as a vehicle for water-soluble compounds. It is generally combined with polymers or gelling agents capable of increasing viscosity and stabilising the emulsion. The lipid phase, on the other hand, contains various plant-derived or synthetic lipids that contribute to the product’s cohesion and influence its sensory profile. The balance between these two phases heavily depends on the emulsifying system, the true linchpin of the formulation : it not only determines the cream’s physical stability but also how the active ingredients are released and perceived on the skin.

Emulsifiers therefore play a decisive role: thanks to their amphiphilic structure, which gives them an affinity for both water and lipids, they stabilise the dispersion of microdroplets of oil in water (or vice versa) and prevent phase separation over time. Thickeners, whether of polymeric, carbohydrate or lipid origin, increase the viscosity of the formulation, thereby improving its stability, sensory properties and the formation of a uniform film on the skin’s surface. Moreover, preservatives curb the proliferation of bacteria, yeasts and moulds that could degrade the product or cause skin reactions, thus contributing to its microbiological safety throughout use. Finally, the adjustment of pH to around 4.5 to 5.5, close to that of the skin, is a crucial parameter for preserving the integrity of the microbiota and avoiding irritation of the epidermis.

Although these excipients often remain invisible to the user, they form the functional architecture of the moisturising cream and determine its stability, tolerability and efficacy.

Moisturising agents: humectants, emollients and occlusives.

Beyond the cream’s structure, its hydrating efficacy primarily relies on three main categories of complementary ingredients : the humectants, the emollients and the occlusive agents. Their combination acts simultaneously on water supply, skin suppleness and reducing water loss, three mechanisms central to maintaining skin hydration. A well-formulated moisturiser combines these various ingredients to best mimic the skin barrier’s natural mechanisms through biomimicry.

• Humectants are molecules capable of attracting and retaining water in the stratum corneum owing to their hygroscopic properties. Among the most commonly used are glycerine, sorbitol, urea and hyaluronic acid. By increasing the epidermal water content, they improve skin suppleness, reduce sensations of tightness and support the proper functioning of enzymes involved in cellular renewal. However, their efficacy is highly dependent on environmental conditions: in very dry atmospheres, they may draw water from deeper layers rather than from the ambient air, which is why it is beneficial to combine them with other types of moisturising agents.

• Emollients, typically composed of plant-derived lipids, fatty esters or butters, act primarily by softening the skin surface and filling the spaces between corneocytes. This action restores the cohesion of the skin barrier, enhances tactile softness and reduces flaking. Unlike humectants, they do not directly increase the water content of the skin but favour a cutaneous environment more conducive to maintaining hydration.

• Occlusive agents, or film-forming agents, form a protective film on the surface of the epidermis that slows the evaporation of water from the stratum corneum. Substances such as petroleum jelly, certain waxes or plant butters are particularly effective at reducing this evaporation and strengthening the skin barrier.

Additives occasionally encountered in moisturising creams.

In addition, some creams contain additives intended to enhance the user experience or protect the product’s integrity over time. For treatments incorporating vegetable oils susceptible to rancidity, antioxidants such as vitamin E, which limit lipid oxidation. Other additives serve primarily sensory functions. Fragrances, for example, provide an olfactory signature favoured by many users, while certain colourants contribute to the product’s visual appeal. However, fragrances can be a source of skin sensitisation, particularly in reactive or contact allergy-prone skin. This is why formulations intended for sensitive skin often favour fragrance-free formulations to reduce the risk of irritation.

The design of a moisturising cream generally relies on a modular architecture, enabling the formula to be adapted to different needs without altering its fundamental structure.

The choice of a moisturising cream is first and foremost determined by its richness, which essentially corresponds to the balance between occlusive agents and humectants.

Dry or mature skin generally benefits from formulations rich in occlusive lipids, which reinforce the skin barrier. Conversely, combination-to-oily skin types favour lighter textures with a higher proportion of humectants to hydrate without intensifying the sensation of an oily film. It is worth noting, contrary to common belief, that oily skin also requires hydration. Indeed, a high sebum production does not mean that the skin contains sufficient water or that its barrier function is effective. The goal for oily skin is to choose a lightweight, non-comedogenic moisturiser, rich in humectants such as glycerine or hyaluronic acid, and lower in occlusive agents to restore cutaneous water balance.

The time of application is also an important criterion. Day creams are generally formulated to absorb quickly, provide a comfortable finish and sometimes incorporate protective agents against external aggressors, such as UV filters. Night treatments, on the other hand, are often richer, taking advantage of the skin’s rest period to support repair mechanisms and strengthen the lipid barrier.

Finally, the active ingredients contained in the cream play a decisive role, as they enable the treatment to be tailored to the skin’s specific needs. A sensitive or redness-prone complexion can thus benefit from soothing ingredients such as Centella asiatica or azelaic acid, which are known to support the skin barrier and limit inflammation. Oily skin types will more readily opt for sebum-regulating ingredients such as zinc. When the objective is to target the signs of ageing, molecules such as retinol can be incorporated into the formulation to stimulate cellular renewal.

Beyond the texture and richness of the moisturising cream, the selection of active substances must not be overlooked for the treatment to effectively address the skin condition.

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