Why do side cheeks hollow on a peanut-shaped face, and why do they bulge when you open your mouth after too much filler?

Director Kim Serim · 2026.10.11

Side cheek hollows on a peanut-shaped face form because fibrous retaining ligaments running from below the cheekbone to the dermis (the zygomatic cutaneous ligament and upper masseteric cutaneous ligament) hold the skin firmly toward the deeper tissue. Because of this pull, filler placed in the hollow tends to spread to the surroundings, and larger volumes make both cheeks bulge when you open your mouth. So at Serene Clinic, we place highly cohesive NEAUVIA filler in small portions, under 1cc in total.

At a glance

Who it's for: Faces where the side cheeks below the cheekbones are depressed, so the contour between cheekbone and jawline looks pinched (peanut-shaped face)
Cause of the hollow: Retaining ligaments below the cheekbone (zygomatic and upper masseteric cutaneous ligaments) anchor the skin toward the deeper tissue
Main product: NEAUVIA (PEG cross-linked hyaluronic acid filler)
Amount: Under 1cc is often enough; decided after an exam
If more is added: Filler spreads to the surroundings, and both cheeks may bulge when you open your mouth
Recovery: Daily activities right away; swelling and bruising last a few days to 2 weeks (varies by person)
Price: Imported NEAUVIA 1cc 550,000 KRW (October 2026 menu)

Why do side cheeks hollow on a peanut-shaped face?

A peanut-shaped face is one where the cheekbones and jawline stand out relatively and the side cheeks between them are depressed, so the facial contour looks pinched in the middle from the front. This depression is not caused only by losing cheek fat.

Facial skin is anchored to deeper tissue by fibrous structures called retaining ligaments. They start from bone or deep fascia, pass through the subcutaneous fat and reach the dermis, holding the skin and soft tissue in place[1][2].

The spot where peanut-shaped side cheeks hollow is where these retaining ligaments are strongly concentrated. The pull on the skin toward the deeper tissue below the cheekbone is strong, so that spot alone sinks in compared with the surrounding tissue.

Which ligaments lie below the cheekbone?

The zygomatic cutaneous ligament starts from bone along the lower border of the cheekbone and the zygomatic arch and runs to the dermis. Furnas described it as anchoring the cheek skin to the lower border of the zygoma just behind the origin of the zygomaticus minor muscle[1]. A representative bundle lies about 4.5cm in front of the tragus of the ear, and another anatomical study measured it at 3.9–4.8cm in front of the tragus[3]. A 2025 histological study confirmed it as a dense bundle of collagen fibers running continuously from periosteum to dermis[4].

The upper masseteric cutaneous ligament is fibrous tissue that starts from the masseter fascia along the front border of the masseter, the chewing muscle, and connects the SMAS (superficial musculoaponeurotic system) to the skin[3][5]. The roughly 3×3.5cm area below the cheekbone where the zygomatic and upper masseteric cutaneous ligaments gather is sometimes called "McGregor's patch"[3], and the gap between the two ligaments has been reported as 13.3mm on average[4].

However, studies describe the exact extent of these ligaments differently, and their position and thickness vary from person to person[3]. So side cheek filler is planned not by fixed coordinates but after checking each person's hollow and where the ligaments pull.

Why do the cheeks bulge when you open your mouth after too much filler?

Because the ligaments hold the skin strongly toward the deeper tissue, the hollow does not rise easily even when filler is placed there. The filler tends to be pushed into the surrounding tissue, where resistance is lower than at the spot the ligaments hold.

If you keep adding volume because the hollow does not fill well, the hollow remains and only the surrounding cheek volume grows. Then, when you open your mouth, the filler built up around it stands out and both cheeks bulge. Director Kim Serim often sees this in patients who had side cheek filler elsewhere.

So side cheek filler is not about filling a set amount. It is a procedure that places small portions so they stay inside the hollow, taking the ligaments' pull into account, and under 1cc is often enough. This is not an area where more filler gives a better result.

Why do we use NEAUVIA filler?

What matters in this area is that the filler stays where it was placed and does not spread, even under the ligaments' pull and the force of chewing.

NEAUVIA is a filler made of hyaluronic acid cross-linked with PEG (polyethylene glycol). What impressed Director Kim Serim most in actual treatments was its cohesiveness. It is not simply a hard gel; it holds together, so even in small amounts there is little sense of it spreading or shifting, and it gave the impression of keeping the designed contour stable.

Even at the same volume, a filler that spreads easily may fail to fill the hollow and only add volume around it. What Serene Clinic looks at when choosing a filler is not how much it fills, but how stably it keeps the shape we first designed.

How is the procedure done?

While you are seated, we check the extent of the hollow and where the ligaments pull, and look at how the cheeks change with the mouth closed and open. Then we mark the injection points.

We minimize pain by using numbing cream together with local anesthetic injections. The filler is not placed all at once; we divide it inside the hollow and check the amount as we go. Any shortfall is corrected with a touch-up after the swelling goes down.

What should I watch out for after the procedure?

You can return to daily activities right away, but swelling and bruising at the injection sites may last from a few days to about 2 weeks. On the day of the procedure, avoid spicy or hot food, alcohol and saunas, and for a few days avoid pressing hard on or massaging your face.

Rarely, if the skin turns white or dark red and pain worsens after filler, it may be a blood vessel problem, so contact the clinic right away. If you are pregnant, have inflammation in the treatment area, or have had other fillers before, please tell us at your consultation.

Prices (as of the October 2026 menu)

Imported NEAUVIA 1cc	550,000 KRW
Imported filler touch-up	150,000 KRW

Prices are per 1cc. The actual amount is decided after an exam based on the extent of the hollow.

Frequently asked questions

Won't it flatten quickly if less than 1cc is used?

The goal of side cheek filler is to fill only the hollow precisely, so the contour changes even with a small amount. How long it lasts varies by area and person, and any shortfall is corrected with a touch-up.

I had side cheek filler before, and my cheeks bulge when I open my mouth.

Filler that has spread to the surroundings may be the cause. We first check the position and amount of remaining filler by touch and ultrasound, and if needed, clear the spread filler before making a new plan.

Will side cheek filler make my face look wider?

It can if more volume is added and the filler spreads around. So we place small portions only inside the hollow and decide the amount while checking the face with the mouth closed and open.

One side cheek is more hollow. Do you inject each side differently?

Most faces have slightly different hollows on the left and right. We do not put the same amount on both sides; we set the position and amount separately to match the difference.

References

This article is general medical information. Results and how long they last vary from person to person. Any treatment can cause side effects such as redness, swelling or pain, so please decide after a consultation.