Collagen for Skin: What a Korean Dermatologist Says Really Works

I'm Dr. Hongseok Kim, a board-certified dermatologist with 21 years of practice and the medical director of VOS Dermatology Clinic in Gangnam, Seoul, right in front of Dosan Park. At VOS I see every patient myself, from the first consultation to the last treatment.

Collagen is the protein that forms the frame of the dermis, and as we age we make less of it and break down more. That is why so many visitors ask me, as a Korean dermatologist, whether collagen for skin, as a supplement, a drink or a cream, will keep their skin firm. This page is based on my YouTube video from February 2024, a long collection of my collagen talks; it summarizes what I explained there for readers abroad, focusing on what you can do yourself and when a clinic treatment makes sense. The video above can be watched with translated captions.

Collagen in a cream: can hydrolyzed collagen reach your dermis?

Short answer: almost certainly not; collagen is far too large, so in a cream it mainly works as a moisturizer on the surface (in the video at 03:51).

Collagen is a protein with a very large molecular weight, around 100,000 daltons. The outer layer of the skin follows what is called the 500-dalton rule: molecules larger than about 500 daltons have great difficulty getting through (in the video at 04:14). That is roughly a 200-fold difference, so for applied collagen to pass the barrier, cross the junction between epidermis and dermis and settle in the dermis is close to impossible.

Cosmetic companies know this, so labels often say hydrolyzed collagen, which simply means collagen broken into pieces (in the video at 05:49). I compare it to the Berlin Wall (in the video at 06:21): when the wall came down, people kept pieces of it, and those stones really did come from the wall, but a stone is not the wall. Hydrolyzed collagen is, more accurately, a mix of peptides (in the video at 09:44). Being smaller, those pieces attract water and can work a little deeper, so the surface feels plumper and smoother. That feeling is real, but it is hydration, not new collagen in the dermis.

Collagen you swallow: what happens after it goes down

Short answer: it is broken down and absorbed as amino acids and small peptides, which your body can use to make its own collagen; the effect is real but modest (in the video at 16:29).

Collagen has a repeating pattern of amino acids, glycine and others, especially proline and hydroxyproline (in the video at 16:42). When you take a collagen supplement, you are not absorbing collagen as it is. Stomach acid and digestion break it down, the gut absorbs amino acids and peptides, and those reach the skin, where cells still have to assemble them into new collagen (in the video at 52:37). That is a long route, so it is natural to ask whether it means anything. Various published papers report better results in people who take it than in those who don't (in the video at 17:32). My own view is that the effect is modest, but better than doing nothing, so I see taking collagen for skin as steady maintenance rather than a fix (in the video at 53:09).

Vitamin C: the part of collagen support people skip

Short answer: your body needs vitamin C to assemble collagen, and it also limits the oxidation that breaks collagen down, so oral vitamin C matters as much as the collagen (in the video at 17:38).

Collagen is built from three amino-acid strands twisted together and then bundled into larger fibres. Vitamin C acts like a gear in that assembly; if the gear is missing, the process stalls. It is also an antioxidant, and oxidation is one of the things that breaks collagen apart after UV exposure. So it helps on both sides: building more and losing less.

In the video I explain that if your goal is collagen, you may need more than the standard daily amount, and I personally recommend a higher intake (in the video at 19:05). Starting high can cause stomach upset or diarrhoea, so build up gradually. If you have a medical condition, are pregnant or take regular medication, ask your own doctor before raising the dose. Where vitamin C fits in the chemistry of building collagen, how collagen differs from elastin, and the debate I had with two fellow dermatologists about oral collagen are on my Korean collagen page.

Protecting the collagen you already have

Short answer: daily sunscreen against UVA, a topical antioxidant, eating lighter and regular moderate exercise protect more collagen than any supplement adds (in the video at 19:50).

UVB is mostly stopped in the outer layer, but UVA penetrates deeply. It does not burn much, yet it keeps raising free radicals and activating MMPs, matrix metalloproteinases, the enzymes that cut collagen. Sunscreen slows that; a topical antioxidant under it handles the UV that still gets through (in the video at 21:00).

Lifestyle matters too, through the fibroblasts that make collagen. Overeating keeps the mitochondria working without rest and raises free radicals, so I suggest eating lighter; simply skipping late-night snacks so you go about ten hours without food overnight can help (in the video at 42:50). Regular, moderate exercise is good, but exercising to exhaustion creates more oxidative stress, so do less, more consistently (in the video at 43:33).

When a supplement is not enough: collagen in the clinic

Short answer: if you need a faster change, treatments either deliver collagen directly or prompt your own cells to make more, and most need repeated sessions (in the video at 53:24).

For years, the ways to raise collagen were creams, supplements and stimulators. Retizen is different: it delivers type I collagen, the type most abundant in skin, directly into the dermis (in the video at 54:08). When I first tried it I worried about immune reactions, as with the collagen injections of the 1980s, but purification has advanced a long way, and in my patients the skin often feels better quickly. One session is not enough; repeated treatment is usually needed. At VOS, Retizen results are typically felt within one to two weeks and last about six months to a year, varying by person.

Collagen stimulators work more slowly but build on your own tissue. Juvelook uses PDLLA with hyaluronic acid to prompt fibroblasts to produce collagen over the following months (in the video at 29:51). For thinner, sensitive skin, Rejuran, a polynucleotide booster derived from salmon DNA, is often considered. If you are comparing options, my overview of Korean skin boosters and my guide to Korean anti aging explain how I layer them. You can also browse creator experiences at VOS. When you message us on WhatsApp, a daylight photo without make-up and your travel dates help me plan.

Results vary from person to person, and whether you need anything beyond daily care is decided at an in-person consultation.

Keep reading on the blog

Lifting & Tightening

Korean Anti Aging: How a Dermatologist Layers Treatments

Korean anti aging, layer by layer: how I combine lifting devices, skin boosters and toxin, what each does, and listed prices. VOS Dermatology, Gangnam.

Sep 29, 2026·7 min read

Skin Boosters & Glow

Korean Skin Boosters: Types, How to Choose, Seoul Prices

Korean skin booster guide: Rejuran, Juvelook, Juveàcell, HILO WAVE and more — how to choose, how they fit a trip and listed prices at VOS Dermatology, Gangnam.

Sep 29, 2026·8 min read

Results, swelling and recovery vary from person to person. This page is general information from VOS Dermatology Clinic based on Dr. Kim's video and does not replace an in-person consultation.