The Science Behind Your Skincare: Why Formulators Choose Gels, Serums, Creams, and Powders

Healthy intact skin is our first line of defense, a selective barrier that does not allow everything to penetrate. So, how do formulas deliver ingredients to the skin? To understand this let’s zoom into the epidermis.

The epidermis is the outermost layer of the skin with a job of a protector from outside invaders (like microorganisms, pollutants etc.), and helps in water retention. The stratum corneum, the skin’s outermost layer, creates a protective seal that locks in water and keeps skin hydrated. This layer is made of keratinocytes (skin cells filled with water-loving molecules) and lipid (oil-loving) molecules

Many skincare formulations have actives, chosen according to their intended benefit like hydration, visible smoothing, luminosity, etc. A carefully selected active can work wonders, let’s explore some of the selection criteria:

Solubility: Water vs Oil

For an active to be able to work, it should be soluble in either of the two phases of the skin (keratinocyte or lipid layer), so that it can penetrate our skin’s surface. This fundamental physicochemical property dictates the ideal vehicle for delivering the ingredients to the skin.

pH:

pH measures how acidic or basic a water-based solution is. Our skin is protected by an acidic layer called the acid mantle, with a natural pH of around 4.5 to 5.5. Skincare products are formulated to match this pH to avoid disrupting the skin barrier. Careful formulation also requires understanding the stability of the actives, as some actives require a specific pH to remain stable and deliver their benefits.

Beyond the Actives:

While actives often steal the spotlight, it's the “base” of a cosmetic product that ensures they perform. The base can be composed of water, oils, emulsifiers, preservatives, and thickeners. A well-formulated base should maintain the formulation’s stability (including its texture, colour, and overall appearance) and safety. Regardless of the actives, an inadequately formulated base can compromise a formula’s overall efficacy. In skincare, it's not just about the stars—it’s about the entire cast working in harmony.

Water:

Water is the primary solvent in most products—creams, gels, and lotions—ensuring smooth texture and effective blending. Humectants like glycerin and hyaluronic acid draw moisture into the skin, enhancing hydration. Emollients, such as shea butter and jojoba oil, soften and smooth by filling gaps between skin surface cells, while occlusive agents like beeswax and silicone form a barrier to prevent water loss. Emulsifiers allow oil and water to mix, creating stable, uniform textures. Thickeners, including xanthan gum and carbomers, provide structure, helping maintain consistency and preventing ingredient separation. Finally, preservatives help ensure the formula stays safe and effective by preventing microbial growth.

Together, these supporting ingredients ensure stability, texture, and performance—allowing the actives to truly shine. However, for this to be true, formulators must ensure that both the actives and the base work in synergy and do not interfere with each other’s activities.

If you love the final feel of your product, thank the formulator. They craft and test each cosmetic to meet quality, safety, and regulatory standards—while tailoring it to your skin type and personal preferences.

The real challenge is creating a formula that satisfies diverse expectations, from texture to performance, all while working within the limits of the active—using a blend of science and artistry to make it happen.

Enhancing absorbance:

Some actives are water-soluble while others are fat-soluble. For a skincare product to deliver its intended benefits, the formulation must spread evenly and be absorbed uniformly across the skin.

To boost absorption of water-soluble actives across the lipid layer of the surface of the skin, formulators might use:

• Lipid encapsulation e.g., liposomes, nano-emulsions

• Penetration enhancers e.g., phospholipids, fatty acids

• Convert them into lipophilic derivatives by modifying the molecular structure of the active.

For fat-soluble actives to be added to watery environments, they might use:

• Emulsifiers for oil-in-water systems,

• Cyclodextrin complexes that trap the lipophilic molecule in a water-compatible shell for water compatibility

• Nanoparticle delivery e.g., nanoemulsions, solid lipid nanoparticles.

Utilizing the science of Rheology

Ever wonder why one serum feels watery while another feels rich? That’s rheology—the science of how creams, gels, and liquids flow and change shape when pressure is applied. In skincare, it’s the secret of adjusting viscosity, texture, and spreadability of the skincare product without altering core ingredients. This magic comes from rheology modifiers like polymers (polyacrylates), thickeners (xanthan gum), and inorganic agents (clays, silica) that can make a formula creamier, thicker, or more structured.

The next time you enjoy the perfect feel of your favorite product, you're experiencing the art of rheology.

To help maintain stability, packaging of the product when properly closed should prevent the infiltration of air or moisture, and should not react with the formulation. Airtight pumps and dark glass bottles are often used to protect products from air and light respectively.

This is also why you see smaller packaging for products like eye creams or lip balms. It's a deliberate choice to ensure you finish the product within its period after opening, helping to protect its efficacy from start to finish.

The science behind this isn't just about texture; it's about molecular size. Lighter, water-based products like serums have smaller molecules therefore can penetrate skin quickly. Conversely, thicker creams contain occlusive agents that form a protective film, locking in moisture but potentially blocking other ingredients.

That’s why the ‘thin-to-thick’ rule matters: apply light products first, then richer creams or oils to seal them in. By layering correctly, you ensure each product can perform its intended function, optimizing the benefits of your skincare routine.

Armed with this knowledge, you can now curate a routine that is not only enjoyable to use but also scientifically optimized for your unique skin. By considering ingredient solubility, skin type, and the "thin-to-thick" layering principle, you can create a regimen where each product works in harmony. This mindful approach transforms your daily routine from a simple habit into a ritual of care, unlocking your skin’s true radiance.