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    Ingredient guide · Ingredient reference

    What should you avoid with peptides? AHAs, vitamin C and product rules

    Peptide compatibility depends on the actual formulation. Some manufacturers advise separating their peptide serums from direct acids and direct vitamin C, with additional restrictions for copper-peptide products. Follow the exact product guidance rather than treating every peptide, acid or vitamin C derivative as interchangeable.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    Read the product-specific exclusions

    The Ordinary advises against combining its Multi-Peptide + Copper Peptides 1% serum with direct acids, direct vitamin C, retinoids and certain strong antioxidants. This is a concrete instruction for that product. It is not proof that every peptide-containing moisturizer has the same restrictions. [1]

    Why direct acids and vitamin C appear on the list

    The manufacturer describes a potential for low-pH conditions to reduce peptide stability and recommends separate routines. AHAs such as glycolic or lactic acid and direct L-ascorbic acid products can be relevant to that advice. A product containing a vitamin C derivative or other type of acid still requires its own instructions. [2]

    Irritation is another consideration

    Even when two ingredients are not specifically prohibited together, the complete routine may be too irritating for an individual. AAD advises cautious product testing and stopping products that cause a reaction. Adding several strong products at once makes the cause harder to identify. [3]

    Build the routine from the labels

    Imagine a copper-peptide serum and a glycolic-acid product both sit in an evening routine. If the peptide manufacturer says to separate them, use different routines as directed rather than inventing a short wait time that supposedly solves incompatibility. Follow a clinician plan when prescription treatments are involved. [1][2]

    Hypothetical example — check a peptide combination
    Product detailPractical question
    Copper-peptide or other peptide formulaWhich instructions apply?
    Direct acid or L-ascorbic acidDoes the manufacturer advise separation?
    Retinoid or strong antioxidantAny additional product restriction?
    Burning or rashStop and reassess tolerance
    What should you avoid with peptides? AHAs, vitamin C and product rules — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. Multi-Peptide + Copper Peptides 1% | The Ordinary
      Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product.
    2. What Are Peptides for Skin? | The Ordinary | The Ordinary
      Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product.
    3. How to test skin care products
      Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product.