Aquaporin and Skin: A Korean Dermatologist on Inner Dryness

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

Aquaporin is the structure I think of whenever patients tell me their skin feels "dry on the inside" even though the surface looks fine. People talk a lot about inner hydration, and aquaporin is the key part that makes it possible. This page is based on my YouTube video from May 2024, rewritten for readers abroad, and the video above can be watched with translated captions.

What is aquaporin?

Aquaporin is a protein that forms a water channel through the cell membrane, so water can pass much faster than simple diffusion would allow (in the video at 00:36).

Scientists used to assume that water spread through the body slowly by diffusion. When they actually measured it, water moved far faster than expected. The structure behind this was described by a chemist who received the Nobel Prize in Chemistry in 2003 for that discovery (in the video at 00:52). The name explains the idea: "aqua" is water and "pore" is a hole, so an aquaporin is a channel protein that opens a pore for water to pass through.

Cell membranes are made of a double layer of lipids, and most substances outside a cell cannot get in. Aquaporins are the exception for water. There are about 13 types, and in our skin we find around six of them: aquaporins 1, 3, 5, 7, 9 and 10. The most common one in skin is aquaporin 3 (in the video at 01:54).

Why the skin surface repels water but the inside needs it

The outer stratum corneum strongly repels water, but once you are past it, the living cells of the epidermis are built to take up and move water (in the video at 02:06).

Think about how wet hands feel uncomfortable. The surface of the skin treats water as something to keep out. The stratum corneum is arranged like bricks and cement, so firmly that even water struggles to pass (in the video at 02:23). That is why getting active ingredients into the skin is such a challenge, and why in dermatology we sometimes use lasers or microneedling to help ingredients past this layer (in the video at 02:43).

Below that wall, things change. I describe the stratum corneum as a castle wall: once you get through it, the village inside is full of activity, with signals passing between living cells. Here, water does not just seep slowly between cells. Aquaporin channels act like a highway, letting around 3 billion water molecules move through per second (in the video at 04:13). When these channels are plentiful and active, the skin has more ways to hold on to water.

Aquaporin and glycerin: more than a water channel

Aquaporin channels also let glycerol pass, and glycerol is one of the substances that helps skin cells hold water (in the video at 04:49).

If you look at a cosmetic ingredient list, after water you will very often see glycerin. Glycerin and glycerol can be treated as the same thing (in the video at 05:08). To understand why it matters, remember how the skin barrier is built: inside the corneocytes there is a natural moisturising factor that pulls in water, and between them sit the intercellular lipids such as ceramides, cholesterol and fatty acids (in the video at 05:19). Sebum on top also contains triglycerides, which are three fatty acids held together by glycerol, and when they break down, glycerol is released.

Glycerol helps keep water inside the corneocytes, so the outer layer can look moist while still repelling water from outside. Aquaporin is one of the routes that glycerol travels through, which is why it plays such a decisive part in keeping skin hydrated (in the video at 06:38). My separate page on skin hydration and whether drinking more water helps explains why water moving into skin is not the same as water staying there.

What weakens aquaporins: UV, poor sleep and blood sugar

UV exposure can break down aquaporins, and a disrupted body clock or high blood sugar is linked to lower levels, which leaves skin drier and more sensitive (in the video at 07:24).

Aquaporins also help to dampen some of the enzymes that UV and other environmental stress switch on, which gives them an antioxidant role (in the video at 07:12). But with a lot of UV exposure, the channels themselves are damaged. With fewer of them, the skin's ability to take up and keep water drops, the barrier weakens, and the skin becomes drier and more reactive. They also matter for wound repair, because a wound needs to recover quickly (in the video at 07:39).

The body clock is another factor. Our circadian rhythm changes hormone release through the day, and aquaporins follow it. When that rhythm is disrupted, for example by poor sleep, aquaporin levels fall and skin water content falls with them, which may be part of why skin looks dull after a bad night (in the video at 07:49). Published research also reports that people with high blood sugar, such as those with diabetes, tend to show fewer aquaporins, and that in dryness, atopic dermatitis, vitiligo and psoriasis these channels can be out of balance (in the video at 08:16). This is an active research area, so treat it as a direction rather than a promise for every patient.

How to look for aquaporin support in skincare

The practical step is simple: look for products that name aquaporin, or check the ingredient list for glyceryl glucoside, which is designed to activate these channels (in the video at 09:38).

Products built around aquaporin usually put the word in their name or description, and more of them have appeared in recent years. When I taught cosmetic science about ten years ago, a few companies were already researching this channel, perhaps ahead of their time (in the video at 09:16). I'm not recommending any brand here. What I want you to remember is the selection criteria: a moisturiser that supports aquaporin, combined with glycerin and barrier lipids, can help both the surface and the inside of the skin.

This matters most during seasonal changes, when big temperature swings between day and night make skin dry and sensitive very quickly (in the video at 10:16). If your dryness keeps returning despite a good routine, it helps to understand how your own skin behaves first; at the clinic we use skin type analysis with VOS Skin MBTI for that. For dry skin that needs more than a cream, my article on PDRN in Korea for dry skin covers clinic options, and my overview of which skin care steps need a dermatologist helps you decide where home care ends. You can also see how visitors combined home care with clinic visits in our creator experiences at VOS.

Results vary from person to person, and the right plan for your skin is decided at an in-person consultation.

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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.