Moisturizers, Oils, and Serums: What’s the Real Difference?
Skincare shelves are overflowing with options; moisturizers, face oils, serums, and ‘essences’ that all promise hydration, radiance, or anti-ageing benefits. But underneath the marketing, these products have distinct functions based on chemistry and how they interact with the skin barrier. Understanding those differences can simplify your routine and help you choose what your skin actually needs.
The Skin Barrier: Where It All Begins
Before talking about product types, it helps to understand what your skin is designed to do. The stratum corneum, the outermost layer of the epidermis, acts as both a protective shield and a moisture-regulating system. It’s made of corneocytes (dead keratinocytes) held together by lipids. Think of it as a brick-and-mortar wall that keeps water in and irritants out (manuscript).
When this barrier is disrupted, water escapes (a process called transepidermal water loss or TEWL), leaving the skin feeling tight, dull, or irritated (review). Effective skincare supports this barrier rather than overloading or stripping it.
Moisturizers: Your Everyday Barrier Support
What They Are
Moisturizers are emulsions (a mix of oil and water) designed to hydrate, seal in moisture, and protect the skin barrier. Most contain a combination of three types of ingredients:
Humectants attract water to the outer layer of skin (e.g., glycerin, hyaluronic acid).
Emollients fill in tiny gaps between cells, creating smoothness (e.g., squalane, fatty acids).
Occlusives form a light seal on the surface to prevent water loss (e.g., dimethicone, shea butter).
Why It Matters
The right moisturizer depends on your skin’s condition, not the latest trend. A well-formulated moisturizer strengthens the lipid matrix, improving resilience and comfort over time.(review)(site)
Serums: Targeted Treatment in High Concentration
What They Are
Serums deliver active ingredients — antioxidants, peptides, or exfoliating acids — in lightweight, water or oil-based vehicles. They’re typically formulated with smaller molecules so they can penetrate more easily into the upper layers of skin. (study)
What They Do
Vitamin C serums protect from oxidative stress and brighten tone.
Peptide serums encourage collagen production.
Niacinamide serums reduce redness and improve barrier function.
Because serums are highly concentrated, they’re used sparingly. One or two drops applied before moisturizer is usually enough.
Key Point
Serums treat; moisturizers protect. One doesn’t replace the other.
Facial Oils: The Barrier Boosters
What They Are
Facial oils are plant-derived lipids — often rich in antioxidants, essential fatty acids, and vitamins — that reinforce the skin’s natural barrier. Unlike moisturizers, they contain no water and typically no humectants.
How They Work
Oils mimic the skin’s natural sebum, reducing TEWL and helping lock in hydration. (study)
Many oils (like rosehip or jojoba) deliver anti-inflammatory and antioxidant benefits. (study)
They’re ideal for sealing in serums or moisturizer, especially in dry climates.
Common Misconception
Oils don’t “moisturize” by themselves. They prevent moisture loss, which is why pairing them with a water-based product increases effectiveness.
How to Layer Them (Without Overdoing It)
A simplified routine that respects the barrier might look like this:
Cleanse Gently. Avoid harsh foaming cleansers that strip lipids
Apply Serum. Choose one targeted to your skin concern (antioxidant in the morning, peptide or retinoid at night).
Moisturize. Hydrate and protect the barrier.
Seal with oil (optional). Especially at night or in dry weather.
If your skin feels greasy or tight after applying products, it’s a sign of imbalance. You may be dealing with too much occlusion or not enough hydration.
Suhu’s Take
At Suhu, we believe that skincare should be grounded in biology, not buzzwords. Moisturizers, oils, and serums all play a role, but understanding why you use each one prevents clutter and confusion.
Our formulations start with science-backed actives and ethically sourced botanicals that strengthen the skin barrier instead of overwhelming it. Whether it’s our Vitamin C Serum or Rosehip Body Oil, each product is built to complement, not complicate, your routine.
