What Are Nasolabial Folds, and Why Do They Deepen?

A nasolabial fold is the crease that runs from the side of the nose to the corner of the mouth. Everyone has one. It is part of how a face smiles, which is why it shows up in photos of children as well as adults. What changes over time is how deep it looks when your face is at rest, and that change rarely has a single cause.

Four things sit behind most deepening folds:

• The skin itself. With age and sun exposure the dermis loses collagen and its natural hyaluronic acid. Thinner, less springy skin creases more easily along a line it folds on thousands of times a day.
• Fat in the cheek. The fat pads of the midface shrink in some places and slide downward in others. When fat gathers above the fold and thins out beside it, the step between the cheek and the upper lip becomes more visible.
• Support that loosens. Small ligaments anchor the cheek tissues to the bone. As they slacken, the soft tissue settles lower and leans on the fold from above.
• Bone that recedes. The bone around the base of the nose and the upper jaw gradually loses projection with age. Less scaffolding underneath means the upper part of the fold can look more hollow.

Expression adds its own layer. People who smile broadly and often fold the skin along the same line many times a day, and genetics decide how full the cheeks were to begin with. Weight loss can also make a fold look deeper almost overnight, because the cheek loses volume while the skin stays the same size.

Why Do Korean Clinics Diagnose the Cause Before Treating the Line?

Because the same-looking line can need completely different treatment. A 2025 case series in Plastic and Reconstructive Surgery Global Open sorted nasolabial folds into skin-type, fat-pad-type, bone-retrusion-type and mixed folds, and its authors used the cause to choose the treatment approach and the severity to decide how much product to use. The authors describe it as a small, short study, so read it as a way of thinking rather than proof, but the logic is the one experienced injectors work by.

In practice, a good consultation for smile lines looks at more than the fold:

• How the fold looks at rest, when smiling and when you lie back, which shows how much is skin, how much is soft tissue and how much is gravity.
• Whether the cheek above it has flattened or dropped, since a fold is often the visible end of a midface change.
• Skin quality, sun damage and how much the skin snaps back when gently pinched.
• Your history: previous fillers, threads or lifting treatments, recent weight change, medications and any tendency to bruise.

Expect the doctor to touch the cheek, ask you to smile and sometimes treat an area other than the fold itself. Supporting the midface can soften a fold indirectly, while filling the line directly in a face whose real problem is sagging can make the area look heavier. Our guide to a first dermatology consultation in Seoul explains what to bring and what to ask in that first meeting.

Which Treatments Do Korean Clinics Use for Smile Lines?

Clinics in Korea generally draw on four groups of treatment, often in combination. What matters is which cause each one addresses.

Fillers are the most direct tool for a fold driven by volume loss. A doctor may place hyaluronic acid deep near the bone at the base of the nose, in the cheek, or more superficially along the line, depending on the cause. Hyaluronic acid fillers can be dissolved with an enzyme called hyaluronidase if needed, which is one reason many doctors prefer them for this area.

Skin boosters are small, spread-out injections that aim to improve the skin rather than the shape. They suit a fine, crepey fold in thin skin far better than a deep one. Our article on Rejuran and polynucleotide skin boosters explains how they work and what to expect.

HIFU and RF devices deliver heat under the skin to encourage tightening. Their effect builds gradually rather than showing on the day, and they work best when laxity, not hollowness, is the main problem. The HIFU lifting guide covers how these sessions feel and who they suit.

Threads are dissolvable sutures placed under the skin to reposition and support soft tissue. Their lift is temporary, and they need careful patient selection. Our Korean thread lift guide goes through types, timelines and limits.

Many plans combine two of these, for example lifting or support in the cheek with a modest amount of filler near the fold. The right mix and order are decisions for the doctor who has examined you.

What Nasolabial Fold Treatments Can't Do

They can't replace surgery for marked sagging. The American Academy of Dermatology notes that non-surgical tightening may not help much when there is a lot of sagging skin, and that surgical lifting gives the most dramatic change. Adding more and more filler to a fold that is really caused by drooping tissue tends to make the lower face look heavier, not younger.

They are temporary. Hyaluronic acid filler is gradually absorbed by the body, lifting effects fade as the face keeps aging, and threads dissolve. Every option needs maintenance at intervals your doctor sets, and the face you are treating will keep changing in between.

Filler in this area carries real risks. The facial artery and its branches run close to the nasolabial fold. According to the US Food and Drug Administration, the most serious risk of dermal fillers is accidental injection into a blood vessel, which can block blood flow and damage tissue, and rare cases have led to vision problems or stroke. That is why this area should be treated only by a qualified doctor who knows the anatomy and has a plan, including hyaluronidase, for managing a blockage. Seek help at once for unusual or severe pain, skin turning white, grey or blue, or any change in vision after an injection.

Not everyone is a candidate. The FDA advises delaying filler while there is active skin inflammation or infection, and caution for people with bleeding disorders or severe allergies; safety in pregnancy and breastfeeding has not been established. Recent weight change, an upcoming event in a few days or unrealistic expectations are also reasons a careful doctor may suggest waiting.

Diagnosis comes first. A fold caused by bone, fat, laxity or thin skin each needs a different answer, and only an in-person examination tells them apart. Sometimes the honest outcome of a consultation is a smaller plan than you expected, or none at all.

Downtime and How to Fit Treatment Into a Trip to Korea

Downtime depends on the treatment and on you, so treat these as general patterns rather than promises:

• Fillers: swelling, tenderness and sometimes bruising for a few days. The shape usually settles over one to two weeks.
• Skin boosters: small bumps or pinpoint marks at the injection points, often fading within a few days.
• HIFU and RF: often little visible downtime beyond redness or tenderness, with changes appearing gradually over the following months.
• Threads: swelling, a feeling of tightness and some restriction on wide mouth opening or facial massage, usually for one to two weeks.

For a trip, a few habits make the difference:

• Book the consultation early in your stay, so you have time to think before agreeing to a plan and the doctor has time to see you again if needed.
• Leave several days between an injectable treatment and your flight home, and ask the clinic how to reach them once you have left.
• Don't stack several new treatments on the same small area in one visit just because time is short.
• Bring a record of any filler or threads you've had before, including the product and date if you know them.

Our guide to booking a skin treatment in Seoul walks through the process from first message to flight home. BeautiPin can also help as its own service: we are a registered foreign patient facilitation agency in Korea, so you can browse the clinics we work with or message us on Instagram, including about a clinic you already have in mind.