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Q322 min at full depthPublished 23 Oct 2026

Do the peptides in a face cream do anything?

The short answer

The evidence is thin. Skin is a good barrier, most peptides are large for it, and many of the studies come from the companies that sell the products.

The short read

  1. The outer layer of skin blocks most molecules above about 500 daltons.
  2. Marketing groups peptides as signal, carrier and relaxing types.
  3. Small trials without strong controls are common; look for independent data.

Cosmetic peptides are marketed as telling skin cells to make more collagen, carrying minerals, or relaxing facial muscles. The difficulty is delivery: the stratum corneum is built to keep things out, and a rule of thumb says compounds heavier than about 500 daltons rarely pass through. Some products use clever carriers or tiny fragments, but independent proof of a visible effect remains limited.

The full explanation

The ingredient list says peptide. The label says it firms, smooths, repairs. What does the science say?

What the marketing claims

Cosmetic peptides are usually sorted into three groups:

  • Signal peptides, said to tell skin cells to make more collagen.
  • Carrier peptides, said to deliver minerals such as copper to the skin.
  • Neurotransmitter-inhibiting peptides, said to calm the nerve signals that cause expression lines.

The barrier problem

The outermost layer of skin, the stratum corneum, is a few cell layers of flattened, tightly packed cells held together by fats. It exists to keep water in and the outside world out. A rule of thumb known as the 500 dalton rule says that molecules heavier than about 500 daltons rarely cross healthy skin. A peptide of six amino acids weighs more than that, often around 800 or 900 daltons.

Makers respond with shorter fragments, fatty tails that help a molecule slip through, or delivery systems packed into tiny carriers. Some of these may help. But reaching the surface layers is not the same as reaching the cells that make collagen.

What the studies look like

Many studies on cosmetic peptides are small, short, and run or paid for by the manufacturer. A common weakness is a missing comparison: a cream with a peptide against the same cream without one. Moisturiser alone can plump skin and make fine lines look smaller within weeks.

How to read a claim

Ask four things. Was there a comparison cream without the peptide? Were the people measuring blind to which was which? Was the study independent? Is the result visible in a photo or only in a measurement? A cream may feel nice and be worth buying for other reasons. Just do not pay extra for the peptide on the strength of the label alone.

Jargon? Say it simply

Education only. Not medical advice, no dosing, no product recommendations. Read this first.

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