Skin has three main layers. The outer layer is a tough barrier that keeps water in and irritants out. The middle layer gives skin its strength and stretch. The deepest layer cushions and insulates.
Most of the middle layer is collagen, a protein that gives skin its firmness, alongside elastin, which lets skin spring back. Both are made by cells called fibroblasts. The outer layer relies on a different protein, keratin, for its toughness.
How skin repairs and renews
Skin replaces itself constantly. When it is damaged, repair follows a set order: bleeding stops, the area is cleaned by the immune system, new tissue and blood vessels form, and finally the new tissue is reorganised and strengthened over weeks to months.
This process is guided by short chains of amino acids that act as signals. When collagen breaks down, some of the fragments themselves tell fibroblasts to make more. From early adulthood, collagen production gradually declines, which is one reason skin becomes thinner and less elastic with age.
Where amino acids come in
- Collagen is especially rich in the amino acids glycine and proline. The body also needs vitamin C to assemble it properly.
- Keratin, the protein of the outer skin layer, hair and nails, is built from amino acids supplied by dietary protein.
- Pigment. Melanin, which gives skin its colour and absorbs ultraviolet light, is made from the amino acid tyrosine.
What influences skin health
- Sun exposure, the biggest external driver of visible skin ageing
- Smoking
- Sleep and stress
- Nutrition, including enough protein and vitamin C
- Hydration and a healthy skin barrier
- Age
This article is for general educational purposes only and is not medical advice.
Frequently asked questions
What is collagen?
Collagen is the main structural protein in skin. It forms a supporting framework that keeps skin firm.
Why does skin change with age?
Collagen and elastin production slow down over time and existing fibres are gradually damaged, so skin becomes thinner, drier and less elastic.
What do amino acids have to do with skin?
Skin's key proteins, collagen, elastin and keratin, are all built from amino acids. The pigment melanin is made from one as well.
How does skin heal after an injury?
In stages: bleeding stops, the area is cleaned, new tissue forms, and the repair is remodelled and strengthened over time.
What is the single most important habit for skin?
Protecting it from excessive sun exposure, which is the largest external cause of visible skin ageing.
Is this medical advice?
No. This article is general educational information. Speak to a qualified healthcare professional about skin concerns.