Which Two Serums Cannot Be Used Together? Guide to Skincare Ingredient Conflicts

Learn which serums should not be used together and why. Expert guidance from Rysun’s research-driven skincare manufacturing team to help prevent irritation and optimize product performance.

Which Two Serums Cannot Be Used Together? Understanding Ingredient Conflicts

With the rising popularity of multi-step skincare routines, consumers are layering several serums at once. However, not all active ingredients work well together. Some combinations can weaken effectiveness, cause irritation, or lead to over-exfoliation.

As a research-driven skincare manufacturer, Guangzhou Rysun Biotechnology Co., Ltd. has over 10 years of formulation experience and a multidisciplinary team specializing in dermatology, chemistry, biology, and pharmacology. Through developing hundreds of serums for 700+ global brands, we’ve gained deep insight into ingredient compatibility.

Below is a clear guide to the serum combinations that should not be used together—and why.

1. Vitamin C + Retinol

Why They Don’t Pair Well

• Vitamin C prefers a low pH environment
• Retinol requires a higher pH to stay effective
• Using them together can reduce the impact of both ingredients

Additionally, both can cause irritation, especially for sensitive skin.

Better Approach:

Use Vitamin C in the morning and retinol at night.

2. AHAs/BHAs + Retinol

Examples:

• Glycolic acid
• Lactic acid
• Salicylic acid
• Mandelic acid

Why They Don’t Pair Well

Both are strong exfoliating ingredients. When layered together, they can cause:

• Excessive dryness
• Redness
• Peeling
• Sensitivity
• Barrier damage

Better Approach:

Alternate days or use acids in the morning and retinol at night.

3. Niacinamide + Pure L-Ascorbic Acid (Unstable Vitamin C)

Why They Don’t Pair Well

Older studies suggested that niacinamide and pure vitamin C may react when combined at high temperatures or unstable formulations. While modern stabilized vitamin C derivatives are compatible, using pure L-ascorbic acid with niacinamide may:

• Reduce brightening efficiency
• Increase chance of redness for sensitive skin

Better Approach:

Use niacinamide with stabilized vitamin C derivatives—a combination our Rysun R&D team often formulates safely.

4. Benzoyl Peroxide + Retinol

Why They Don’t Pair Well

This pairing can cause:

• Skin irritation
• Excessive dryness
• Reduced retinol stability
• Inflamed breakouts due to barrier disruption

Better Approach:

Alternate: benzoyl peroxide during the day, retinol at night.

5. AHAs/BHAs + Vitamin C

Why They Don’t Pair Well

Both pure vitamin C and exfoliating acids require acidic environments, but layering them can:

• Trigger irritation
• Cause stinging
• Disrupt the skin barrier

Better Approach:

Use Vitamin C alone in the morning and acids on alternate nights.

Why These Combinations Matter in Formulation

At Rysun Biotechnology, our Research Institute ensures ingredient combinations are scientifically compatible before entering production. Our team evaluates:

• pH levels
• Stability of active ingredients
• Irritation potential
• Penetration depth
• Market requirements across different countries

This allows us to create gentle yet effective formulations, meeting global standards and preventing problematic ingredient interactions.

Safe and Effective Combinations We Often Recommend

Some ingredients pair very well and deliver enhanced benefits. Rysun frequently formulates these combinations:

• Niacinamide + Hyaluronic Acid (hydration + barrier support)
• Vitamin C derivatives + Niacinamide (brightening synergy)
• Retinol + Hyaluronic Acid (reduced irritation)
• Peptides + Hyaluronic Acid (firming + moisture)

Our extensive formulation experience ensures these combinations are optimized for performance and low irritation.

FAQs

1. Can I use two serums at the same time?

Yes, as long as the ingredients are compatible and not overly irritating.

2. Are all forms of vitamin C incompatible with niacinamide?

No. Stabilized derivatives like SAP, MAP, and VC-IP are safely combined with niacinamide — a pairing Rysun often formulates.

3. What are the safest serums to layer?

Hyaluronic acid, peptides, ceramides, and panthenol are generally safe with most actives.

4. How can consumers avoid irritation when layering?

Start slowly, alternate days, and use soothing ingredients like HA or centella.

5. Do all markets prefer the same serum combinations?

Not always. Rysun adjusts formulations by region—humid, dry, sensitive-skin, or brightening-focused markets have different preferences.