◆ IDUN Journal

Face Oils vs. Serums: What the Science Actually Says

By Siu Lie Tan, Founder · 6 min read

They are not rivals so much as different tools. The confusion comes from marketing, not biology.

Walk any beauty aisle and you will be asked to choose between a serum and an oil as though they were opponents. They are not. They do different jobs, and the more useful question is not "which is better" but "which does what."

What a serum is

A serum is usually a water-based concentrate built to carry water-soluble actives — think vitamin C, niacinamide, hyaluronic acid — into the upper layers of the skin. Its texture is light because water is its main ingredient. That is also its limitation: to stay stable and pleasant, most serums are largely water, with the active present in modest proportion.

What a facial oil is

A facial oil is lipophilic — it speaks the skin barrier’s own language. The outer layer of skin is built of cells held together by a lipid matrix; the whole structure is fat-loving by design. A well-chosen oil is rich in fatty acids, antioxidants and fat-soluble vitamins, and it works with that matrix rather than against it: reinforcing the barrier, slowing water loss, and carrying fat-soluble botanicals to where they are useful.

The myth that oils "just sit on top"

The most persistent misconception is that oils cannot absorb. In reality, oils composed of smaller fatty acids interact readily with the skin’s own lipids; what people perceive as "sitting on top" is often simply an oil that has done its barrier work and left a protective finish. The barrier is not a wall to be breached — it is a system to be supported, and supporting it is precisely what a good oil does.

A serum feeds the water side of the skin. An oil tends the lipid side. Skin needs both — but only one of them repairs the barrier.

When a concentrated oil is the smarter choice

If your concern is barrier resilience, dryness, sensitivity, elasticity, or delivering fat-soluble botanicals — an oil is the right tool. And here concentration matters. Many products described as "treatments" are mostly water and filler, with the working ingredients present in small amounts.

001 was built as the opposite: a concentrate, not a lotion. No water pretending to be treatment, no fillers standing in for substance — a dense blend of botanical oils where each earns its place. A few warmed drops are enough, which is also why a small bottle lasts. In IDUN’s testing, that concentration translated into a measured 18.04% improvement in skin elasticity over four weeks — the barrier, supported, doing what it is built to do.

The honest summary: use a serum for water-soluble actives if you like one; use a true oil to repair and hold the barrier. If you keep only one step, make it the one that tends the structure everything else depends on.

This article is for general educational purposes and is not medical advice. IDUN's cited results (+18.04% skin elasticity, +10.71% hair density at four weeks) reflect IDUN's own product testing. For a medical concern, consult a qualified professional.