Gouri PCL: What New Research Says About Collagen and Bruising

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.

Gouri PCL is one of the skin boosters getting the most attention right now, and two questions come up about it: does it really make collagen, and what about the bruising? Whenever I hear "this injection makes collagen," I want to know whether there is evidence, and by what route. This page is based on my YouTube video from September 2026, where I went through the 2025–2026 research on liquid PCL; I rewrote it for readers abroad. The video above can be watched with translated captions.

What is Gouri PCL, and does PCL turn into collagen?

Short answer: no; PCL is not collagen's raw material, and new collagen forms as your tissue reacts to it.

PCL stands for polycaprolactone, a biodegradable polymer (in the video at 00:42). A common misunderstanding is that PCL placed in the skin simply changes into collagen. It doesn't. When a foreign material enters tissue, the body does not sit still: proteins attach to its surface, immune cells respond, macrophages get involved, and the signals passing back and forth change the fibers, the cells and the extracellular matrix (ECM). The part we care about for skin is that new collagen forms in that process.

So the accurate way to put it is not "PCL becomes collagen" but "PCL triggers a tissue response, and new collagen forms as fibers, cells and ECM change" (in the video at 01:31). The PCL itself does not stay forever either; it breaks down gradually through hydrolysis. At VOS, Gouri is the liquid-type PCL collagen stimulator I use for elasticity, fine lines and texture.

What do the latest studies on liquid PCL show?

Short answer: the early data point the right way, but they are not yet enough to call the clinical effect proven.

A study published in 2026 injected liquid PCL into animal skin that had been photoaged with ultraviolet light (in the video at 01:53). In the treated group, dermal thickness and collagen density increased, and COL1A1 expression and type I collagen, which had dropped with photoaging, moved clearly toward recovery. But this was an animal study. What it tells us is that liquid PCL may induce biological responses related to collagen formation in tissue. It cannot be stretched to say that the same change happens in people.

That is why human studies matter. In 2025, a study treated the midface of 30 people with liquid PCL twice and observed them for six months, assessing skin condition, before-and-after change and patient satisfaction (in the video at 02:41). Because of its size and design, a 30-person study alone cannot establish the clinical effect. My summary: preclinical work shows tissue-level change, early human data are starting to appear, and larger studies with independent repetition are still needed.

Why does Gouri under the eyes bruise more easily?

Short answer: under-eye skin is thin and its blood vessels are complex, so a needle or cannula can more easily injure a small vessel.

In 2026 there was also a pilot study applying liquid PCL around the eyes, with only three participants, reaching the forehead and under-eye area with a cannula (in the video at 03:18). Whatever the effect, bruising is a separate issue you cannot ignore in this area.

When a needle or cannula damages a small vessel, blood leaks out and seeps into the surrounding tissue (in the video at 03:53). A bruise starts red or purplish-blue and turns green, yellow and brown over time. Macrophages clear the red blood cells; inside them, hemoglobin breaks down, and an enzyme called heme oxygenase turns heme into biliverdin, which is green. Another enzyme, biliverdin reductase, turns that into bilirubin, which is yellow. The iron released is not thrown away: macrophages recover it for reuse or store it as ferritin or hemosiderin, and hemosiderin left in tissue gives brownish tones (in the video at 05:02). Not everyone goes through the same color order, but the color keeps changing with time.

Why do some Gouri bruises last for months?

Short answer: a 2026 report of seven cases suggested that liquid PCL may slow the clearance of blood pigments, but this is still a hypothesis.

The report analysed seven cases in which a bruise after liquid PCL injection lasted a long time (in the video at 05:41). The researchers proposed that the structure liquid PCL forms in tissue may hold blood-derived pigments and delay their normal removal. Put simply, the focus shifts from the bleeding itself to how the pigment is cleared. They were clear that this is a hypothesis built from cases, not a proven mechanism (in the video at 06:25). In thin skin like the under-eye area, they also raised the possibility that light scattering, the Tyndall effect, makes the area look bluish, in addition to what remains in the tissue. The authors described this as an uncommon phenomenon.

From the patient's side, the practical question is how to tell an ordinary bruise from one that will linger (in the video at 07:02). A bruise keeps changing over two or three days, one week, two weeks: the color shifts, it fades and the area shrinks. That is blood being processed normally. If clear time has passed and it still looks blue or blue-gray with little change, check with the clinic that did your treatment.

How were the long-lasting bruises treated?

Short answer: with lasers, light and hyaluronidase injections, and all seven cases improved, though it took from about 5 days to 3.5 months.

The seven cases were treated with a range of methods, including 532 nm picosecond and 1064 nm picosecond lasers, IPL, Nd:YAG and hyaluronidase injections (in the video at 07:43). The time to final improvement ranged from about 5 days to 3.5 months. That period was counted from the start of treatment, not from the day of the PCL injection, so the total can be longer. Because it is a collection of cases, it is not a trial comparing one treatment against another. What matters is that, with time, all seven resolved.

Should bruising stop you from having liquid PCL?

Short answer: no; the more useful step is choosing technique that keeps vessel injury to a minimum and knowing what to watch for.

The most important thing is a technique that minimises damage to blood vessels (in the video at 08:35). Being afraid of a lingering bruise is not a reason to give up on the treatment altogether. In my view, liquid PCL's main strength is that it firms collagen and improves texture without building visible volume. The practitioner's job is to inject carefully to avoid bruising so patients are not inconvenienced; your job, if a bruise does appear, is to watch whether it is fading or staying the same. Even a bruise that stays was treatable in the published cases.

The video does not cover the number of sessions, intervals or cost; at VOS those are confirmed at consultation. If you are still comparing booster types, my video note on whether a hyaluronic acid skin booster counts as a filler explains the other main category, and my guide to types of Korean skin boosters and how to choose and my breakdown of how much product a Korean skin booster plan really uses cover the wider picture. For one patient's experience, see the review of a mother's Gouri and Belotero Revive skin booster case in Seoul. You can also read creator experiences at VOS.

Results, timing and recovery vary from person to person, and the right plan for you 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.