What Is Collagen, What Does It Do? Types, and Its Place in Skin and Hair

Collagen is not a single molecule but a protein family with at least 28 defined types. If you think of the dermis as a fabric, collagen is its threads: it lets the skin withstand stretching and keeps its tissue intact. Collagen on a product label and collagen in the skin do not do the same job. To understand the difference, you first need to look at their structure.

Triple helix: The structure that makes collagen collagen

Three protein chains wind around each other like a rope. The chains repeat a glycine-X-Y pattern. Because glycine is the smallest amino acid, it allows the helix to pack tightly, and at positions X and Y prolines and hydroxyprolines are frequently found. Hydroxyproline keeps the helix from falling apart at body temperature. The enzyme that forms it requires vitamin C, and this is why skin becomes fragile in scurvy.

In the dermis, collagen is produced by cells called fibroblasts. The cell first makes the precursor molecule procollagen and secretes it; outside the cell this molecule is cut and matures, then the molecules bind together to form fibres and fibre bundles. A single natural collagen molecule is about 300.000 daltons in size, far larger than the substances that can pass through the intact skin surface.

Which collagen type is where in the skin?

Several types work together in the skin. Percentages vary with the measuring method and age, so they should be read as ranges.

Proportions also change with age: in foetal skin type I is about 70-75%, rising to 85-90% in adults. Types with a small share do not have a small role. Type VII collagen's inherited defect causes dystrophic epidermolysis bullosa, a disease in which the epidermis cannot anchor to the dermis, leading to blisters in the skin. The "collagen" mentioned in creams usually does not make these distinctions.

Does hair contain collagen?

The hair strand itself is largely made of keratin; collagen is not the building block of hair. Collagen's connection to hair is around the root, not the strand. Type XVII collagen plays a role in protecting the stem cells of the hair follicle. In a 2016 study with mouse and human tissue, the breakdown of this protein with age was shown to lead to loss of stem cells and shrinking of the follicle. This is basic research; it does not show that applied or ingested collagen changes this process.

Hydrolyzed collagen in shampoos and creams works differently. In studies dated 1977 and 1991, fragments of around 1.000-3.000 daltons were seen to attach to damaged or permed hair. This is a surface care effect; it does not show that it lengthens hair or reduces shedding. Current and independent data are also scarce.

Why does it decline with age and sun?

• Production slows. Skin collagen peaks in the twenties. After that, a production decline of roughly 1-1,5% per year is often cited, but this figure comes from a review linked to the supplement industry and should not be treated as a precise measure. In a more concrete comparison, in the skin of people over 80, type I procollagen, the indicator of collagen production, was found to be about 68% lower than in the 18-29 age group.
• Cells are less stretched. Between the fibres that break and become disorganised, the rate of fibroblast surface contact with collagen dropped from 78% to 58%. A cell that is not stretched enough produces less. The same study attributes the decline both to the cell's own ageing and to this mechanical effect.
• Menopause accelerates it. In the first 15-18 years after menopause, an average annual decrease of 2,1% in skin collagen has been reported. In men, the hormonal decline is slower, so this sudden acceleration is not seen.
• Sun increases breakdown. Within 8 hours after UV, the genes of MMP-1, MMP-3 and MMP-9 enzymes begin to work. Type I procollagen falls in the same period, and by 24 hours it nearly disappears from the upper dermis.
• Sugar hardens bonds. Advanced glycation end products (AGEs), which attach to collagen fibres, accumulate over time, stiffening the fibre and reducing its function.

Some of the factors on this list cannot be changed, but sun can be. That is why the most studied step for protecting collagen is daily sunscreen. A broad-spectrum product of at least SPF 30 is renewed every 2 hours and after sweating or swimming. On the production side, retinoids and vitamin C have been most studied. In small studies, retinol increased procollagen in older forearm skin, while vitamin C is an essential auxiliary for collagen-producing enzymes. None of these fully restores collagen that has been lost.

How does hydrolyzed collagen differ from natural collagen?

In cosmetics, collagen is generally not used in the same form as in the skin. The molecule is broken into small pieces by hydrolysis or produced by recombinant methods. Knowing the difference between the three helps you read the name on the label correctly.

Animal collagen carries species-specific regions and can vary between batches; recombinant production aims to reduce these problems. What hydrolysed collagen does in a cream, the funding debate in supplement studies, and the question "does collagen cream work?" are explained in detail in the collagen creams article.

Substances confused with collagen

• Elastin: A separate protein that lets the skin return to its former state after stretching. Collagen gives strength; elastin gives elasticity.
• Gelatin: Collagen whose helix has been disrupted by heat. It comes from the same source but does not carry the same structure.
• Peptide: A short chain of amino acids. Label names beginning with "Palmitoyl" are not collagen; they are suggested to be able to act as signals.
• Hyaluronic acid: Not a protein but a sugar chain. It is found in the same tissue as collagen and holds water.

If hydrolysed collagen comes from an animal source, this may need to be found out from the ingredient information or the manufacturer. If you are allergic to fish or another animal product, read the label. Test a new product first on the inner arm or elbow crease, twice a day, for 7-10 days.