What is the composition of a moisturizing cream?

The use of cosmetics dates back several millennia. The earliest documented evidence appears around 6,000 years ago in ancient Egypt, where ingredients like aloe vera were already employed to protect the skin, increase its suppleness, and mitigate signs of aging. The Egyptians also used fragrant oils and ointments to cleanse the skin, mask body odors, and shield themselves from the intense sun and dry desert winds. These practices were later transmitted to the Greek and Roman civilizations, laying the foundations for the skincare methods we know today.

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

A moisturizing cream: first and foremost, a structured emulsion.

From a physico-chemical standpoint, the vast majority of moisturizing creams are emulsions, that is, stable mixtures of two normally immiscible phases : an aqueous phase and an oily phase. This arrangement allows hydrophilic and lipophilic substances to be delivered to the skin simultaneously, supporting both the 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 called direct emulsions, are the most common in cosmetics because they leave a light finish without a noticeably greasy film and promote relatively fast 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 night or for the very dry skin.

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

Excipients, essential yet often overlooked.

Beyond its emulsion structure, a moisturizing cream relies on a set of excipients essential for its long-term stability and good skin tolerance. These substances, most of which lack biological activity, nevertheless serve crucial functions. Some enable the homogeneous mixing of the aqueous and oily phases, others maintain viscosity, while still others prevent microbial contamination, help adjust 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 determine the product’s texture, ease of application, and shelf life. The aqueous phase, which predominates in many creams, forms the base of the formula and serves as a carrier for water-soluble compounds. It is typically combined with polymers or gelling agents that increase viscosity and stabilize the emulsion. The lipid phase, on the other hand, contains various plant-derived or synthetic fats that contribute to the product’s cohesion and affect its sensory properties. The balance between these two phases relies heavily on the emulsification system, the true linchpin of the formulation : it dictates not only the physical stability of the cream but also how active ingredients are released and perceived on the skin.

Emulsifiers therefore play a critical role: thanks to their amphiphilic structure, which gives them an affinity for both water and lipids, they stabilize the dispersion of oil microdroplets in water (or vice versa) and prevent phase separation over time. Thickeners, whether polymeric, carbohydrate-based, or lipid-derived, increase the formulation’s viscosity, enhancing its stability, sensory properties, and the formation of a uniform film on the skin’s surface. Additionally, preservatives limit the growth of bacteria, yeasts, and molds that could degrade the product or trigger skin reactions, thus contributing to the microbiological safety of the treatment throughout its use. Finally, the adjustment of pH around 4.5 to 5.5, close to that of the skin, is a crucial parameter for preserving the integrity of the microbiota and preventing irritation of the epidermis.

Even though these excipients often remain invisible to the user, they constitute the functional architecture of the moisturizing cream and determine its stability, tolerability, and also its efficacy.

Hydrating agents: humectants, emollients, and occlusives.

Beyond the cream’s structure, hydrating efficacy rests primarily on three major categories of complementary ingredients : the humectants, the emollients and the occlusive agents. Their combination enables simultaneous action on water supply, skin suppleness, and the reduction of water loss—three mechanisms at the core of maintaining skin hydration. A well-formulated moisturizing cream combines these ingredients to best mimic the natural functions of the skin barrier through biomimicry.

• Humectants are molecules able to attract and retain water in the stratum corneum thanks to their hygroscopic properties. Among the most commonly used are glycerin, sorbitol, urea, or hyaluronic acid. By increasing the water content of the epidermis, they improve skin suppleness, reduce feelings of tightness, and support the proper functioning of enzymes involved in cellular renewal. However, their efficacy is highly dependent on the environment: in very dry conditions, they may draw water from deeper skin layers rather than from the ambient air, which highlights the importance of combining them with other types of moisturizing agents.

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

• Occlusive agents, also known as film-forming agents, create a protective film on the surface of the epidermis that slows water evaporation 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 moisturizing creams.

Additionally, some creams contain additives intended to enhance the user experience or to protect the product’s integrity over time. For treatments containing plant oils that are prone to rancidity, you will often find antioxidants, such as vitamin E, which limit lipid oxidation. Other additives serve primarily a sensory function. Fragrances, for instance, provide an olfactory signature appreciated by many users, while certain colorants contribute to the product’s visual appeal. However, fragrances can be a source of skin sensitization, especially in individuals with reactive or contact-allergy–prone skin. That is why formulas made for sensitive skin often favor fragrance-free formulations to reduce the risk of irritation.

The design of a moisturizing cream typically relies on a modular architecture, enabling the formula to be adapted to various needs without altering its fundamental structure.

The selection of a moisturizing cream is based primarily on its richness, which essentially corresponds to the balance between occlusive agents and humectants.

Dry or mature skin generally benefits from formulas rich in occlusive lipids that strengthen the skin barrier. Conversely, combination-to-oily skin favors lighter textures with a higher proportion of humectants to hydrate without accentuating the greasy film sensation. It should be noted, incidentally, that, contrary to a common misconception, oily skin also needs hydration. Indeed, significant sebum production does not mean the skin contains enough water or that its barrier function is fully effective. The goal for oily skin is to choose a lightweight, non-comedogenic hydrating cream rich in humectants such as glycerin or hyaluronic acid, and lower in occlusive agents to restore the skin’s water balance.

The timing of application is also a crucial criterion. Day creams are typically formulated to penetrate rapidly, deliver a comfortable finish, and sometimes include protective agents against external aggressors, such as sunscreen filters. Night treatments, conversely, are often richer, taking advantage of the skin’s rest phase to support repair mechanisms and strengthen the lipid barrier.

Finally, the active ingredients in the cream play a decisive role, as they allow the treatment to be tailored to the skin’s specific needs. A sensitive or redness-prone skin can thus benefit from soothing ingredients, such as Centella asiatica or azelaic acid, known for supporting the skin barrier and reducing inflammation. Oily skin types will preferentially turn to sebum-regulating actives such as zinc. When the goal is to target signs of aging, molecules such as retinol can be incorporated into the formula to stimulate cellular renewal.

Beyond the texture and richness of the moisturizing cream, the selection of active ingredients should not be overlooked to ensure the treatment effectively addresses the specific skin concern.

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