The Science of Oxidation: How Skincare Ingredients Degrade Over Time

When most people think about skincare "going bad," they imagine spoilage — mold, bacteria, or unpleasant smells. But one of the most common and invisible forms of product breakdown isn’t always microbial. It’s chemical.

This quiet process is called oxidation — and it's happening to many active ingredients long before you notice any change in your product’s appearance.

In this post, I want to take you inside the science of oxidation, and explain why freshness plays such a critical role in preserving potency.

What Is Oxidation?

At its simplest, oxidation is a chemical reaction that occurs when certain molecules react with oxygen — either from the air or from the water within the formula itself. This reaction can lead to:

• Loss of activity (the ingredient no longer performs as intended)

• Color changes

• Off-odors

• Formula destabilization

• Reduced efficacy for your skin

Oxidation doesn’t always make a product unsafe — but it absolutely can make it far less effective.

For skincare that relies on delicate actives, oxidation is one of the biggest challenges formulators must manage.

Which Ingredients Are Most Vulnerable to Oxidation?

1. Antioxidants

Ironically, the very ingredients designed to protect your skin from oxidative damage are some of the most vulnerable to oxidation in the bottle.

• Vitamin C (Ascorbic Acid): Extremely oxidation-prone; rapidly degrades when exposed to air, light, or heat.

• Coenzyme Q10: A powerful antioxidant that gradually loses potency once oxygen permeates the formula.

• Resveratrol, Green Tea Extract, and Polyphenols: Naturally sensitive to oxidation, light, and time.

2. Botanical Oils

Plant oils contain fatty acids that can oxidize, leading to rancidity and loss of nutritional value.

• Polyunsaturated oils (such as Rosehip, Evening Primrose, Sea Buckthorn) are rich in skin-loving fatty acids but have shorter oxidative shelf lives.

• Oxidized oils may smell off, feel sticky, or worsen barrier function if heavily degraded.

3. Water-Based Actives

Many water-soluble vitamins and extracts are also vulnerable:

• Vitamin B3 (Niacinamide): Relatively stable but can degrade under improper storage.

• Vitamin B5 (Panthenol): Stable but sensitive to repeated heating and poor formulation.

• Peptides: Can lose structural integrity over long storage periods or under high-heat conditions.

4. Peptides and Proteins

Peptide stability depends on pH, formulation environment, and storage. With prolonged exposure to oxidative conditions, certain peptide chains can break down and lose efficacy.

How Oxidation Happens Over Time

Even in a sealed jar, oxidation can still slowly occur because:

• Oxygen is trapped in headspace (the empty air inside the bottle).

• Oxygen can slowly permeate through certain packaging materials.

• Light and heat can accelerate oxidative reactions.

• Larger manufacturing runs often sit in bulk storage tanks for months before filling.

In mass-market production, a product may be manufactured 6–12 months before you ever open it — and oxidation may already be silently degrading some of its actives.

Why Freshness Directly Affects Potency

At Botanical Atelier, oxidation is one of the key reasons I work in small batches and keep my formulas as fresh as possible.

• The less time ingredients sit, the less opportunity oxidation has to occur.

• Small batch production means ingredients are exposed to air and heat fewer times during manufacturing.

• Gentle preservation allows actives to remain active, while still ensuring microbial safety.

• Seasonal production lets me source ingredients closer to harvest, when their phytochemical activity is at its peak.

Freshness isn't simply a marketing word — it’s a functional design strategy that helps preserve the potency of delicate actives, ensuring that when you apply your skincare, your skin receives the full intended benefit.

Freshness is Potency.

Oxidation is happening behind the scenes whether you can see it or not. This is why freshness matters so much, and why I take such care in how I source, handle, and formulate each product inside the Custom Oil Lab.

Because when you invest in active skincare, you deserve ingredients that are still alive, still potent, and still capable of delivering results.