Face Serum — How to Choose the Right One and When You Can Skip It

What is a serum and why is it different from a cream?

A serum is a product with a lightweight, liquid or gel-like texture that contains a higher concentration of active ingredients than a moisturising cream. While a cream serves a protective and moisturising function (forming an occlusive film), a serum delivers active ingredients directly into the skin.

The key difference lies in the formula: a serum contains no heavy emollients or occlusives (petrolatum, silicones, rich oils), which allows the active ingredients to penetrate deeper and faster. The concentration of actives in a serum is typically 5–20%, whereas in a cream it is 0.5–3%.

Popular serums and their active ingredients

Vitamin C (L-Ascorbic Acid)

A vitamin C serum is one of the most thoroughly researched antioxidants. The effective concentration is 10–20% L-Ascorbic Acid at a pH of 2.5–3.5 (a low pH is essential for stability and penetration). Vitamin C brightens hyperpigmentation, stimulates collagen synthesis and protects against photoageing.

Limitations: L-Ascorbic Acid is unstable — it oxidises when exposed to light and air (turning brown). More stable derivatives (Ascorbyl Glucoside, Sodium Ascorbyl Phosphate) are gentler but less effective. Check the form of vitamin C in your serum in our ingredient encyclopedia.

Retinol and vitamin A derivatives

Retinol is the gold standard of anti-ageing — it accelerates cell turnover, stimulates collagen, and reduces wrinkles and hyperpigmentation. The effective concentration is 0.3–1.0% for retinol, though beginners should start with 0.1–0.3% and gradually increase frequency.

Newer derivatives — Retinal (retinaldehyde) and Hydroxypinacolone Retinoate (HPR) — work faster or more gently than retinol. Retinol is applied in the evening (it is photolabile) and requires mandatory SPF in the morning.

Niacinamide (Vitamin B3)

Niacinamide is a versatile ingredient: it regulates sebum, reduces hyperpigmentation, strengthens the skin barrier and has an anti-inflammatory effect. The optimal concentration is 2–5% — higher concentrations (10%) are not proportionally more effective and may cause irritation. It is well tolerated by most skin types and compatible with most active ingredients.

Hyaluronic Acid

A hyaluronic acid (HA) serum is a humectant — it draws water into the skin. The most effective formulas combine different molecular weights of HA: high-molecular-weight HA (>1000 kDa) forms a moisturising film on the surface, while low-molecular-weight HA (50–300 kDa) penetrates deeper. HA alone does not moisturise the skin — it needs a source of water (humidity in the air or an occlusive cream applied on top).

AHAs/BHAs

A serum with glycolic acid (AHA) or salicylic acid (BHA) is a liquid chemical peel. These exfoliate, even out skin tone and prevent blackheads. They are used 2–3 times a week, not daily. Do not combine with retinol in the same evening routine.

Layering — how to combine serums?

Layering means applying several serums one on top of another. The rules:

1. From the lightest to the thickest — apply a water-based serum before an oil-based one.
2. From the lowest pH to the highest — vitamin C (pH 3.0) before niacinamide (pH 5.5–7.0).
3. Do not combine in a single application: vitamin C with retinol, AHA/BHA with retinol, or glycolic acid with niacinamide at a very low pH.
4. You can combine: hyaluronic acid with virtually anything, niacinamide with retinol (despite old myths), and vitamin C in the morning + retinol in the evening.

In practice, 2 serums is a sensible maximum — each additional layer reduces the penetration of the previous one. More than 3 serums is usually marketing, not dermatology.

When can you skip a serum?

A serum is not mandatory. You can skip it when:

• Your skin is healthy, hydrated and needs no correction — a good moisturiser + SPF will suffice.
• You have a minimalist routine — cleansing + a cream with SPF is a solid base. A serum adds value, but it is not the foundation.
• Your skin barrier is damaged — active ingredients (retinol, acids, vitamin C at a low pH) can worsen the condition of damaged skin. First rebuild the barrier with a simple ceramide cream, then introduce active serums.
• You use a cream with active ingredients — if your face cream contains 0.3% retinol or 5% niacinamide, an additional serum with the same ingredient is unnecessary.

What to look for when choosing a serum?

1. The concentration of the active ingredient — the manufacturer should state it. No information likely means a low concentration.
2. The position on the INCI list — the active ingredient should appear in the upper half of the list, not right at the end.
3. The form of the ingredient — e.g. L-Ascorbic Acid vs. Ascorbyl Glucoside is a difference in both efficacy and stability.
4. The packaging — vitamin C and retinol require light-protective packaging (dark glass, an airless pump). A clear jar means the ingredient will degrade.

Check every active ingredient in your serum in our ingredient encyclopedia — you will find out whether the concentration makes sense and whether the form is effective.

Summary

A serum is a powerful skincare tool, but not a magic elixir. An effective serum has the right concentration of the active ingredient, a stable form and is matched to the skin's needs. More serums does not mean better skin — the key is the conscious choice of 1–2 products that address specific concerns. And if your skin is healthy and needs no correction, a cream with SPF is enough.

Related articles

• Facial cleansing — oil, gel, foam or micellar water?
• Double cleansing — is double cleansing necessary?

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