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Facial serum was, for a long time, my blind spot.
When I started learning cosmetic formulation, I assumed it was simple — mix two or three oils, maybe a drop of vitamin E. That was my version of a serum. I had no idea there were five completely different types, each built on a different base, each working differently on the skin.
What shifted my thinking wasn’t just formal education. It was the contrast. After 25 years in the oil and gas industry, I started reading conventional serum ingredient lists — and I recognised half of them from work. Mineral oil. Petrolatum. PEG emulsifiers. Same industry, different bottle.
That’s when the question became interesting: if the base changes everything — how a serum absorbs, what it does for the skin, what it leaves behind — then picking a serum is actually a formulation decision. Not a shopping one.
This post breaks down five serum types by base, not by trend. Once you understand the format, the rest of the choice becomes obvious.
If you’re new to ingredient-focused skincare, my DIY Skincare Ingredients guide explains how different bases and actives behave on the skin. If you’re interested in using or making serums in a practical way, this topic naturally connects to my DIY Skincare Recipes, where ingredient logic turns into real formulations. The way we choose and use serums influences how much we buy, keep, and eventually discard, which directly ties into broader sustainable beauty practices.
| Aspect | Explanation |
|---|---|
| What is a facial serum? | A concentrated skincare product designed to deliver active ingredients in a lightweight format |
| How serums work | Focus on ingredient concentration rather than heavy occlusion |
| Why ingredients matter | Different ingredient bases target different skin concerns |
| Common active ingredients | Vitamin C, hyaluronic acid, bakuchiol, niacinamide |
| Skin concerns addressed | Dehydration, dull skin, uneven skin tone, acne, fine lines, early signs of aging |
| Oil-based serums | Lipid-based formulas that support the skin barrier and reduce moisture loss |
| Gel-based serums | Water-rich formulas with humectants and gelling agents for lightweight hydration |
| Water-based serums | Serums built on hydrosols or water with humectants and water-soluble actives |
| Emulsion serums | Lightweight blends of oil and water that combine hydration and nourishment |
| Pressed balm serums | Solid serums made from butters, waxes, and oils for intensive nourishment |
| What serums can’t do | Replace an entire skincare routine or work as miracle products |
| How to choose a serum | Based on ingredients, concentration, and skin type — not trends |
WHY INGREDIENT CONCENTRATION MATTERS IN A FACIAL SERUM
A serum’s job is precision. Ingredients like vitamin C, hyaluronic acid, bakuchiol, or niacinamide perform best when they’re not buried under heavy textures or diluted by unnecessary fillers.
Higher concentration doesn’t automatically mean better results. Always follow the manufacturer’s recommended usage rate for each active — going above it rarely improves performance and often causes irritation. Skin responds to balance, particularly when it’s sensitive or reactive.
The serum format allows actives to reach the skin more efficiently than a cream or lotion. That’s its structural advantage — but only when the concentration is right.
Harvard Health Publishing notes that serums are not designed to replace a full routine or fix everything at once — they provide targeted support where the skin actually needs it. Chosen for what they contain rather than how they’re labelled, serums are precise tools.
How to Use a Facial Serum in a Simple Skincare Routine
A serum belongs close to the skin — applied after cleansing, before heavier products. This placement allows actives to absorb without being blocked by thicker textures.
In practice:
- Apply on clean, slightly damp skin. Water-based and gel serums spread more evenly and absorb more comfortably this way.
- Layer light to rich. If you use more than one serum, water-based or gel formulas go first, oil-based or emulsion serums after.
- Use less than you think. A few drops or a small pump is enough. More product doesn’t improve performance.
- One serum, one purpose. Combining multiple serums works only when each has a clear, distinct role. When in doubt, fewer layers produce calmer skin.
If you want to try an oil-based serum at home, my Nourishing Facial Oil recipe is a good starting point.
Types of Facial Serums (Based on Formulation)
1. Oil-Based Serums
An oil-based serum contains no water and no gelling agents. It works entirely through lipids — botanical oils selected for their fatty acid profile, absorption speed, and skin affinity.
The function is barrier support and moisture retention, not direct hydration. The oil doesn’t add water to the skin — it slows down how fast the skin loses it. Botanical oils including jojoba, sunflower, and argan support barrier repair through their fatty acid composition — oils higher in linoleic acid show better barrier repair potential than those dominant in oleic acid [Lin TK et al., PMID 29947134]. For oil-soluble actives, bakuchiol at 0.5% reduces wrinkle surface area and hyperpigmentation comparably to retinol 0.5%, with significantly better tolerability [Dhaliwal S et al., Br J Dermatol 2019, DOI: 10.1111, BJD 16918].
Sustainability choices are especially visible in oil-based serums — upcycled carrier oils repurposed from food industry by-products fit naturally into this format. More on that in my Upcycled Oils in Skincare guide. How botanical oils differ by fatty acid composition — and why that matters for barrier function — is covered in my Fatty Acids Profile in Skincare and Unsaponifiables in Botanical Oils guides. For a broader overview of available oils and how they differ, see my Botanical Oil Guide. If you’re unsure whether to choose refined or unrefined, Refined Oils in Skincare and Unrefined Oils for Skincare explain the difference and when each makes sense.
Best for: dry, mature, environmentally stressed skin. Also suitable for oily or acne-prone skin when lighter, fast-absorbing oils are selected.
If you’d rather buy than formulate, Sisley Black Rose Precious Face Oil is a good example of a botanically-based oil serum.
2. Gel-Based Serums
Gel serums are water-rich formulas structured with gentle gelling agents — no oils, no waxes. They feel almost weightless on application, absorb quickly, and leave no lipid film behind.
Niacinamide performs well in this format. At 2%, it measurably reduces sebum excretion rate in Japanese subjects and casual sebum levels in Caucasian subjects across separate clinical trials [Draelos ZD et al., PMID 16766489]. It also significantly increases stratum corneum hydration through lipid matrix reorganization [Bochenek K et al., PMC11811021, 2025].
Gel serums work best when skin needs hydration without lipid weight. They layer easily under richer products and tolerate warmer climates better than oil-heavy formats.
Best for: oily, combination, or acne-prone skin; warmer weather; minimalist routines.
3. Water-Based Serums
Water-based serums are built on water or hydrosols and work primarily through humectants — ingredients that draw moisture to the skin’s surface rather than nourishing the lipid barrier.
Hyaluronic acid molecular weight matters here. Low molecular weight HA (50 kDa) increases skin hydration by up to 96% and penetrates the stratum corneum — a meaningful distinction from larger HA molecules that stay at the surface [Papakonstantinou E et al., Dermatoendocrinol 2012, PMC3583886].
Because these serums contain water, they require proper preservation. Best made in small batches or sourced from formulators with documented stability testing. The broader behaviour of hydrosols and other water-soluble ingredients is covered in my DIY Skincare Ingredients guide. For humectants specifically, my Glycerin guide explains how water-binding ingredients function in aqueous formulas.
Best for: dehydrated or sensitive skin; routines where lightweight hydration is the priority.
If you’d rather buy than formulate, Kiehl’s Powerful Strength Line Reducing Concentrate is a good example of a water-based active serum.
4. Emulsion Serums
An emulsion serum sits between a classic serum and a light lotion. It combines water and oils in a stable, lightweight formula — delivering hydration and lipid support in one step, without the heaviness of a cream.
Plant phospholipids fuse with the stratum corneum’s lipid layer, enhancing barrier integrity and reducing inflammatory response [PMC5796020, 2018].
Emulsifier selection matters more here than in simpler formats. Conventional emulsion serums often rely on PEG emulsifiers — PEG-20, PEG-40 — produced through ethoxylation, a process that generates 1,4-dioxane as a by-product. A known carcinogen, banned under EU Cosmetic Regulation 1223/2009 Annex II [SCCS 2015]. Plant-derived alternatives — lecithin, oligosaccharide-based emulsifiers — do the same structural job without that contamination risk.
Emulsion serums require more formulation precision than simpler formats. The underlying logic is explained in my DIY Skincare Ingredients guide.
Best for: combination, balanced, or seasonally changing skin; skin that needs both hydration and nourishment without heavy texture.
If you’d rather buy than formulate, Filorga NCEF Revitalize Serum or Biotherm Life Plankton Regenerating Serum are worth considering.
5. Pressed Balm Serums
A pressed balm serum is water-free and solid — made from botanical oils, plant butters, and waxes. Its job is to reduce moisture loss and reinforce the lipid barrier through a concentrated protective layer.
Because there’s no water phase, every ingredient contributes directly to structure, texture, and skin function. A clinical study combining melatonin, bakuchiol, and ascorbyl tetraisopalmitate in a night serum-in-oil format showed statistically significant reduction in wrinkles (11%), increase in skin firmness (8%), and reduction in redness (70%) after 12 weeks [Goldberg DJ et al., PMID 30924254].
Conventional pressed balm formulas often use paraffin wax — a petroleum refinery by-product. Plant-derived waxes such as candelilla or carnauba perform the same structural role without the petroleum origin. Plant butter selection determines texture and melt behaviour — covered in depth in my Ultimate Guide to Botanical Butters. For oil selection within this format, my Botanical Oil Guide and Fatty Acids Profile in Skincare explain how lipid composition affects barrier performance.
Pressed balm serums are also the most packaging-efficient format in this category — solid, no pump mechanism, no dropper, minimal waste.
Best for: dry, sensitive, or environmentally stressed skin; cold weather; evening routines; low-waste skincare.
ECOLOGIST’S TAKE
The serum category has a packaging problem that rarely gets discussed — and a chemistry problem that gets discussed even less.
Most conventional serums are built on petroleum derivatives. Mineral oil is a crude oil distillate. Petrolatum is a refinery by-product. PEG emulsifiers are produced through ethoxylation — a process that generates 1,4-dioxane as a by-product. A known carcinogen, banned under EU Cosmetic Regulation 1223/2009 Annex II [SCCS 2015]. New York State independently set a 10ppm limit for cosmetics in 2022.
I spent 25 years working with these exact compounds in the oil and gas industry. Seeing them in skincare ingredient lists was not a surprise. It was a recognition.
Botanical alternatives exist for every single one of them. Jojoba and squalane replace mineral oil. Shea and mango butter replace petrolatum. Lecithin and oligosaccharide-based emulsifiers replace PEG compounds. The performance is comparable. The environmental footprint is not.
On packaging: the ratio of packaging to product in the serum category is high — small glass vials, dropper bottles, pump dispensers. Oil-based and pressed balm serums are the most efficient formats. Water-free, longer shelf life, and in the case of pressed balm — no pump or dropper mechanism at all.
Format choice has consequences beyond the skin. That’s worth factoring into the decision.
How to Choose the Right Serum Based on Ingredients
Stop thinking in terms of “best” — think in terms of what the skin actually needs right now. For a detailed breakdown of which oils are less likely to clog pores, see my Comedogenic Rating guide.
- Dry or dehydrated skin: Oil-based, emulsion, or pressed balm serums. The priority is barrier support and moisture retention.
- Oily or acne-prone skin: Gel-based or water-based serums. Lightweight hydration without lipid loading.
- Sensitive skin: Short ingredient lists, gentle bases. Water-based or carefully formulated oil serums are the safer starting point.
- Mature or environmentally stressed skin: Emulsion or oil-based serums. Both hydration and lipid nourishment, without heavy texture.
Facial Serum FAQs
Do facial serums actually work?
Yes — when chosen based on ingredients and skin needs. Facial serums work by delivering active ingredients in a concentrated, lightweight format, but they are not miracle products and work best as part of a consistent skincare routine.
Are facial serums really necessary?
Facial serums are not strictly necessary, but they can be very helpful for targeting specific skin concerns such as dehydration, uneven skin tone, or early signs of aging. They add precision to a routine rather than replacing other steps.
Can a facial serum replace a moisturizer?
No. A facial serum delivers active ingredients, while a moisturizer helps seal hydration and support the skin barrier. They serve different roles and work best together.
What’s the difference between oil-based and water-based serums?
The base determines what can go into it, how it absorbs, and what it does for the skin. Oil-based serums support the lipid barrier and reduce moisture loss. Water-based serums attract and hold water at the skin’s surface. Both are useful — for different skin needs and different points in a routine.
Final Thoughts: Ingredients Come Before Formulation
Five formats, five completely different formulation logics. A gel serum and a pressed balm serum share almost nothing except the word “serum” on the label. The base determines the chemistry, the preservation needs, the skin compatibility, and — something most guides don’t mention — the environmental footprint of what you’re putting on your face.
That’s why I formulate with botanical oils and butters. Not as a trend, but as a logical choice — once you know what the alternatives are made of.
My advice: pick one format that matches your skin’s current state. Not the most expensive, not the most trending. The one whose base makes sense for what your skin actually needs right now. One serum. One clear purpose.
The rest follows from there.
For the formulation side, DIY Skincare Ingredients covers how each base behaves in practice. Ready to make your own? The DIY Skincare Recipe Library is the next step.
