Why Serums, Creams, and Oils Perform Differently

Skincare products come in many formats: watery serums, rich creams, pure oils, lightweight lotions, thick balms. These aren’t interchangeable delivery systems. The format you choose affects how ingredients perform, how deeply they penetrate, and what your skin ultimately receives.

Understanding Product Formats

Each format has a distinct structure that determines its behaviour on skin.

Serums

Typically water-based with high concentrations of active ingredients and minimal occlusive or moisturising components. They’re designed to deliver specific actives rather than to moisturise.

Characteristics:

• Lightweight, fast-absorbing texture
• High concentration of targeted ingredients
• Low in heavy emollients and occlusives
• Designed to layer under other products

Best for: Delivering water-soluble actives (vitamin C, hyaluronic acid, niacinamide) at higher concentrations than creams typically offer.

Creams and Lotions

Emulsions combining water and oil phases, held together by emulsifiers. Creams are thicker (more oil); lotions are lighter (more water).

Characteristics:

• Provide hydration and some occlusion
• Can deliver both water-soluble and oil-soluble ingredients
• More comfortable as standalone products
• Layer less well than serums

Best for: General moisturising, delivering moderate concentrations of various actives, occlusion without heaviness.

Oils

Pure oils or blends, sometimes called oil serums or facial oils. Contain no water phase.

Characteristics:

• Highly occlusive
• Can only deliver oil-soluble ingredients
• Create a barrier layer on skin
• Don’t provide water-based hydration

Best for: Sealing in previous layers, delivering oil-soluble actives (retinol, vitamin E), protecting compromised barriers.

Gels

Water-based but thickened with gelling agents rather than emulsifiers. No or minimal oil content.

Characteristics:

• Lightweight feel, often cooling
• Quick absorption
• No occlusive properties
• Suitable for oily or acne-prone skin

Best for: Hydration without weight, delivering water-soluble actives to oily skin types.

Balms

High-oil or wax-based products with minimal or no water content. Thicker than oils.

Characteristics:

• Very occlusive
• Slow to absorb, may leave residue
• Excellent for barrier protection
• Limited ability to deliver water-soluble actives

Best for: Barrier repair, overnight treatment, very dry or damaged skin.

How Format Affects Penetration

The format determines which route ingredients take into your skin.

Water-Based Formats

Aqueous serums and gels rely on ingredients being able to penetrate in their water-dissolved form. This works well for small, balanced molecules but poorly for highly lipophilic ingredients.

Hyaluronic acid, for instance, is typically delivered in aqueous serums. Larger molecular weights remain on the surface, providing hydration but not penetrating. Smaller weights can penetrate slightly deeper but still primarily work in the stratum corneum.

Oil-Based Formats

Oils and anhydrous serums excel at delivering lipophilic ingredients. Retinol, for example, penetrates more effectively from an oil base than from a water base because it can dissolve into the lipid matrix of the stratum corneum.

However, oils alone can’t deliver water-soluble ingredients. A pure oil with niacinamide listed wouldn’t be delivering that niacinamide effectively — it can’t dissolve in oil.

Emulsions as Compromise

Creams and lotions can deliver both types of ingredients because they contain both water and oil phases. The trade-off is typically lower concentrations of each compared to targeted serums.

The emulsion structure also affects release — ingredients must partition out of the cream matrix and into skin. This can be slower than from a simple serum.

Concentration Considerations

Format affects how much active ingredient you’re actually receiving.

Serums are typically formulated with higher active concentrations (10-20% vitamin C, 5-10% niacinamide) because they’re small-volume products designed for potency.

Creams usually contain lower active concentrations (1-5% of most actives) because they need to balance moisturising function, stability, texture, and cost across a larger product volume.

Oils vary widely — some are pure single ingredients (100% squalane), while oil serums might contain 1-5% of specific oil-soluble actives like retinol.

This concentration difference is why a serum containing 15% vitamin C will generally outperform a moisturiser containing 2% vitamin C for vitamin C-specific benefits.

Layering and Sequence

Format determines how products layer.

Aqueous serums absorb and leave little residue, allowing subsequent products to penetrate. Apply first.

Light gels and lotions absorb well and can follow serums without issue.

Heavier creams absorb more slowly and begin to occlude. Apply after serums but before oils.

Oils and balms create barriers that prevent subsequent product absorption. Apply last.

Breaking this sequence — applying oil before serum, for instance — means the serum sits on top of the oil barrier rather than absorbing into skin.

Occlusion and the Barrier Question

Occlusion — creating a physical barrier that reduces water loss — is a property of oil-rich formats.

High occlusion: Petroleum jelly, balms, heavy oils, water-in-oil emulsions Moderate occlusion: Creams, silicone-based products Low/no occlusion: Serums, gels, toners

Occlusion has value: it helps maintain hydration, supports barrier repair, and can enhance penetration of certain ingredients by increasing skin hydration.

But occlusion also has downsides for some skin types: it can feel heavy, contribute to congestion in acne-prone skin, and prevent beneficial exposure to air.

The right level of occlusion depends on your skin’s needs and the climate you’re in.

Format and Stability

Some actives are more stable in certain formats.

Vitamin C (L-ascorbic acid) is notoriously unstable. Aqueous formulations degrade faster than anhydrous ones. This is why some vitamin C products use oil-soluble derivatives or anhydrous (water-free) formulations.

Retinoids are sensitive to light and oxygen but relatively stable in both oil and emulsion bases when properly protected.

Peptides are generally stable in aqueous formulations but may degrade in very acidic products.

Format choice isn’t just about texture preference — it affects whether the active ingredient remains active through the product’s life.

When Format Matters More Than Ingredients

Here’s an underappreciated reality: a well-formulated product in an appropriate format often outperforms a poorly formulated product with “better” ingredients.

A 10% vitamin C serum in a properly stabilised aqueous base at correct pH will outperform a 20% vitamin C cream where the vitamin C has oxidised due to poor formulation.

A retinol oil that delivers 0.5% retinol effectively will outperform a retinol serum where the retinol isn’t properly solubilised or protected.

Format enables ingredient performance. Without the right delivery system, even the best ingredients underperform.

Choosing the Right Format

Match format to purpose:

For targeted treatment: Serums deliver actives most efficiently. Use serums for your primary concerns (pigmentation, fine lines, hydration).

For daily moisturising: Creams and lotions provide balanced hydration and some active delivery. Good for maintaining results rather than achieving them.

For barrier support: Oils and balms provide occlusion and deliver lipophilic repair ingredients. Best for damaged barriers or very dry skin.

For oily skin: Gels and lightweight serums provide benefits without weight or pore-clogging occlusion.

For dry skin: Creams and oils provide the occlusion and emollient content dry skin needs.

The Multi-Format Routine

Most effective routines combine formats strategically:

1. Cleanser (format: gel, cream, or oil)
2. Toner/essence (format: aqueous)
3. Treatment serum (format: targeted to the active)
4. Moisturiser (format: cream or gel based on skin type)
5. Oil or balm if needed (format: occlusive)
6. Sunscreen (format: cream, gel, or fluid)

Each format serves a purpose. Eliminating one category might not matter for some skin types; for others, it leaves a gap.

Practical Takeaways

Don’t assume all formats are equivalent. A niacinamide serum, niacinamide cream, and niacinamide oil (if such a thing existed sensibly) would deliver the ingredient differently at different concentrations with different skin effects.

Match format to ingredient: water-soluble actives in aqueous bases, oil-soluble actives in oil bases, both in well-formulated emulsions.

Layer by format: watery to oily, permeable to occlusive.

Consider format when comparing products. A £15 serum might deliver an active more effectively than a £50 cream containing the same ingredient at lower concentration in a less efficient delivery system.

The format isn’t just packaging for ingredients — it’s an integral part of how those ingredients reach your skin and whether they do any good when they get there.