[Dr. Bellevue Column 106.] Oily on the Outside, Dry on the Inside? Get Seborrheic Dermatitis Under Control with This

Hello,

Bellevue Clinic, dedicated to everyone’s beauty,

Dr. Bellevue is pleased

to greet you again today.

When meeting patients in the consultation room, I often hear certain skin concerns repeated.

“Doctor, by the afternoon, oil is running down my forehead and around my nose, but my skin feels so tight inside that it feels like it could tear.”

“When I apply matte foundation because my skin is oily, white flakes show through. But when I use something moisturizing, my makeup starts sitting on top of my skin and completely breaks down within an hour.”

“Breakouts keep appearing, so I carry oil-absorbing sheets everywhere. Why are my cheeks itchy and dry?”

These are typical examples of what is commonly called “oily but dehydrated” skin. Why does this contradictory condition—shiny on the outside but parched on the inside—occur? Many of you likely already know that simply changing cosmetics or cleansers, or using oil-absorbing sheets, cannot solve the problem.

In today’s column, I would like to discuss the pathophysiological causes of this “dehydrated skin” and Rejuran, a skin booster that may fundamentally reset it.

1. The real reason skin is shiny on the outside but parched inside: “compensatory sebum secretion”

The epidermis and stratum corneum, the outermost layers of our skin, act as a protective barrier that preserves moisture. In the dermis beneath them, the extracellular matrix (ECM), including hyaluronic acid, collagen, and elastin, should be densely arranged to retain moisture.

But what happens if frequent peeling, excessive cleansing, UV exposure, aging, or aftereffects of laser procedures loosen the density of the dermis and damage the skin barrier? Moisture inside the skin rapidly evaporates into the air, increasing transepidermal water loss. At this point, the skin sounds an emergency alarm to protect itself.

“Since all the moisture inside is evaporating,

let’s at least cover it with a layer of oil!”

The sebaceous glands then begin producing sebum excessively. This is known as “compensatory sebum secretion.” The resulting effects and the vicious cycle of skin damage proceed as follows:

• Without enough moisture, the skin feels extremely tight and stings inside—dehydrated skin

• Excess sebum is secreted on the surface, clogging pores and causing small bumps and acne

• To eliminate the shine, the face is cleansed more aggressively, stripping away too much oil

• The barrier breaks down further, worsening inner dryness and causing sebum production to surge even more

Therefore, the oil flowing on the surface is not a sign that the skin is moisturized. You can think of it as “the skin crying out for help.” Rather than repeatedly wiping or washing away the oil, you need to normalize the structure inside the dermis and the barrier itself to break this vicious cycle. It is also not uncommon for increased sebum production to progress into seborrheic dermatitis. You may wonder why seborrheic dermatitis is being mentioned here, but in many actual cases, the symptoms of seborrheic dermatitis begin with inner dryness. Of course, the conditions for developing the disease must also be present. I hope those with seborrheic dermatitis understand that addressing inner dryness can also be an important step toward improvement.

※ Those with symptoms of seborrheic dermatitis, please take note!

1. Excess sebum is a necessary condition—the “soil”—for seborrheic dermatitis

Increased sebum does not mean that seborrheic dermatitis will develop in 100% of cases, but without sebum, seborrheic dermatitis does not develop either. This is why it is limited to areas with well-developed sebaceous glands, such as the scalp, T-zone, glabella, and sides of the nose. Sebum production itself provides the “environment” in which the condition can develop.

2. Malassezia yeast—the catalyst, or “trigger,” of inflammation

• Lipophilic fungus: Malassezia is part of the normal skin flora and feeds on sebum. Therefore, reducing sebum also reduces the fungus. It is similar to how mold is much less likely to grow when a bathroom floor is thoroughly washed after a shower and the moisture is dried. Just as drying water, soap, and sebum residue from the body after showering removes the environment needed for mold growth, you need to improve inner dryness and the oil-moisture balance to block the sebum—the “food” for the fungus.

• Production of free fatty acids: Malassezia breaks down triglycerides secreted by the sebaceous glands using the enzyme lipase, producing free fatty acids such as oleic acid and arachidonic acid.

• Induction of inflammation: These breakdown products irritate the stratum corneum and damage the epidermal barrier, triggering inflammatory reactions such as redness, itching, and scaling.

The biggest mistake people with seborrheic dermatitis make is focusing solely on “removing oil” or “controlling inflammation.” However, if the inner dryness caused by a barrier weakened by inflammation is not addressed, the skin continues producing more sebum to protect itself. This creates a vicious cycle in which the inflammation does not disappear and becomes more severe. In other words, rather than forcibly wiping away surface oil or focusing exclusively on inflammation management with steroids, normalizing skin regeneration and the moisture environment inside the skin may be an important key to treating or managing seborrheic dermatitis. Ultimately, addressing the underlying cause is important.

2. Why choose Rejuran (PN) instead of cosmetics?

High-priced essences and moisturizing creams applied to the skin’s surface have large molecules and cannot reach deep into the dermis. They may temporarily form a barrier that prevents moisture evaporation, but they cannot make the damaged dermal environment repair itself.

Rejuran is a cell-regenerating substance that restores the weakened skin’s own regenerative capacity, which is why it is highly recommended for dehydrated skin.

★ PN (Polynucleotide), with high biocompatibility

A purified, high-molecular-weight biological complex extracted from salmon DNA. It is heat-stable and has very little risk of immune rejection.

★ Restoring dermal density—ECM remodeling

PN injected directly into the dermis stimulates fibroblasts, promoting new synthesis of collagen, elastin, and glycosaminoglycans. It fills out thinned and loosened dermal tissue, restoring its role as a “sponge” capable of retaining moisture.

★ Normalizing the oil-moisture balance

When the skin’s ability to retain moisture within the dermis is restored, it no longer needs to produce excessive sebum. Sebum production naturally decreases, reducing surface shine and breakouts.

★ Improving skin-barrier thickness and reducing redness

By strengthening the junction between the epidermis and dermis as well as the skin barrier, Rejuran fundamentally reduces sensitivity that causes the skin to redden and react easily to external irritation.

3. Pain that brings tears to your eyes—why patients still come back

To be honest, Rejuran can be fairly painful because a highly viscous, high-molecular-weight substance must be injected densely, point by point, into the sensitive upper dermis rather than the epidermis. It is true that some reviews say, “I ended up shedding tears during the procedure,” or “It hurt so much that I almost stopped halfway.”*

Nevertheless, the rate of repeat procedures among people who have experienced Rejuran is exceptionally high. This is because the perceived skin changes are strong enough to more than offset the intense discomfort. Patients who have undergone the procedure commonly describe the following changes one to two weeks afterward:

• “My face no longer feels tight even if I don’t apply toner immediately after cleansing.”

• As the moisturizing structure is replenished from within the dermis, the first noticeable change is often the disappearance of the desert-like tightness inside the skin.

• “It’s past 3 p.m., and I don’t even need to use oil-absorbing sheets.”

• “As sebum becomes regulated, my makeup breaks down less and the darkening that used to occur is significantly reduced.”

• “My foundation adheres to my skin like sticky rice cake.”

• “My rough, dull skin texture is refined, fine lines are softened, and the way my base makeup adheres is completely different.”

• “My skin tone looks clearer, and I can feel that my skin’s basic resilience has become stronger.”

• “My sensitive skin, which used to react easily to a little seasonal wind or dust, now holds up firmly.”

In other words, Rejuran is a procedure that raises the skin’s damaged “basic strength” from the foundation up, making the discomfort worthwhile. Still, if you really dislike pain… another method must be found.

4. Dr. Bellevue’s recommendation—How should Rejuran be administered?

★ Recommended treatment plan

Although many people notice an improvement in skin texture after just one session, a cumulative course of approximately three to four treatments at two- to three-week intervals is recommended for complete remodeling of the damaged dermis. Afterward, maintenance treatment once every four to six months can help maintain a healthy skin barrier for a longer period.

★ Tips for reducing discomfort

If you are very afraid of experiencing the pain each time repeated treatments are needed, you can choose Rejuran HB Plus, which combines a local anesthetic ingredient, lidocaine, with hyaluronic acid. Alternatively, the procedure can be made more comfortable by allowing sufficient time for numbing cream application and using a precision injector device to significantly reduce discomfort.

Are you trapped in a vicious cycle where your skin is an oil-producing country on the outside but drying out like a desert within? Before struggling with sebum and inflammation, have the dermal environment inside your skin properly assessed. When the foundation inside your skin becomes healthy and strong, your skin’s radiance and oil-moisture balance will naturally follow. Thank you for reading this long post!

This procedure may be accompanied by temporary redness, swelling, bruising, or other effects depending on the individual, so a thorough consultation with a medical professional is required.

For office workers who have difficulty finding time on weekdays due to their busy daily schedules, Bellevue Clinic near Gangnam Station provides regular consultations and treatments on Sundays and public holidays to help make weekend care more convenient. Please note, however, that every Wednesday is a regular closure day when arranging your schedule. At Bellevue Clinic, where procedures are performed safely, we hope you can maintain firm, clear, and transparent-looking skin even during the hot month of August. Thank you!

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With the Mark-Vu skin diagnostic examination, you can check various skin concerns at once, including skin texture, pigmentation, pores, wrinkles, skin tone, dark circles, radiance, redness, melanin, sebum, and acne-causing bacteria—many of which are difficult to identify with the naked eye.

Bellevue Clinic scientifically analyzes the skin, makes a final diagnosis of the necessary procedures when needed, and strives to provide the most effective and helpful treatments for each patient through kind and detailed consultations.

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