Custom serum formulation

The category where active choice, stability and sensory feel collide most directly — and where most formulation problems in market originate.

Serums are where brands concentrate their claims, which is also why they are where formulation goes wrong most visibly. A serum is usually a thin, fast-absorbing system carrying actives at meaningful use levels, and almost every difficult decision in the category is a trade between how well an active performs, how stable it stays, and how the product feels going on.

Most serum failures in market are stability failures that were predictable at the bench. Discolouration, separation, loss of potency and pH drift are not random events — they follow from decisions about the active system, the vehicle and the packaging that were made months before anyone noticed a problem.

The other constraint is sensory. A serum that performs and feels unpleasant will not be repurchased, and "feels unpleasant" usually means tacky, pilling, or leaving a film under makeup. These are formulation outcomes, not accidents, and they can be designed for deliberately rather than discovered after a sampling round.

What makes this category difficult

Vitamin C oxidationL-ascorbic acid is effective and notoriously unstable, and browning is the visible end of a process that started well before the colour changed. The decision is usually between accepting a shorter shelf life, moving to a derivative with different performance, or engineering the vehicle and packaging around the raw acid.
pH conflicts between activesActives frequently want incompatible conditions. Combining them in one product means either compromising on the pH each prefers, separating them across a routine, or reformulating around derivatives that tolerate a shared environment.
Peptide and PDRN handlingThese systems are sensitive to how the rest of the formula is built — preservative choice, pH and processing temperature all matter. Use level also has to be honest: a peptide present below a meaningful concentration is a marketing claim, not a functional ingredient.
Retinoid stability and toleranceRetinoids degrade with light, air and heat, and the tolerance profile is as commercially important as the potency. A product that works and causes irritation gets returned.
Sensory and layering behaviourTack, pilling and behaviour under makeup or sunscreen are the complaints that show up in reviews. They are formulation decisions — polymer choice, film formers, humectant load — not fixed properties of the category.

Formats developed

Water-based serums
Cream-gel serums
Oil serums and biphasic systems
Ampoules and essences
Anhydrous active systems

Before you write the brief

Settle these and the first conversation goes considerably further.

Which single claim the product is being bought for
Which actives are non-negotiable to your positioning, and at what use level
Target texture and finish — and what your customer is already using it alongside
Packaging direction, since it constrains what is formulable
Target cost-per-unit and intended retail price

Common questions

Can you combine vitamin C and niacinamide in one serum?

Yes, and the idea that they cannot be combined is largely a persistent myth built on conditions that do not reflect a well-built formula. The real question is whether the combination is stable in your specific system and at your specific pH, which is a formulation question rather than a rule.

Why did my existing serum turn brown?

Most often oxidation of an active — vitamin C being the common culprit — accelerated by air ingress, light, temperature or a chelation gap. It is diagnosable, and the fix depends on the cause rather than on swapping ingredients until the colour holds.

How high can an active concentration go?

Higher is not automatically better and past a point it buys irritation rather than efficacy. The useful target is the level supported by evidence and tolerated by your customer, which is frequently lower than what competitors put on the front of the bottle.

How to work on this

Bespoke formulationOriginal formulas developed to your brief — texture, sensorial, actives, claims and price target. Not a stock base with your fragrance dropped in.Reformulation & rescueFormula failing stability, feeling wrong on skin, costing too much, or needing an ingredient swapped out? Existing products get diagnosed and fixed.

Related categories

Moisturizers & creamsEmulsions are the most sensory-driven category in skincare and the least forgiving of shortcuts in how the base is built.

Working on a serums?

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