Under-Eye Skin Booster: The Concentration Matters More Than the Product

Under-Eye Skin Booster: The Concentration Matters More Than the Product

Let me get straight to the point.

With under-eye Skin boosters, what matters most isn't which product you use —

it's the concentration at which it's injected that determines your results.

Let me explain exactly why.

Did You Think All Under-Eye Skin Boosters Were the Same?

Under-eye Skin boosters work by injecting PN (polynucleotide) or HA (hyaluronic acid) directly into the Dermis,

improving the skin's texture, thickness, and moisture retention from within.

Unlike under-eye Filler — which is often grouped together with Skin boosters —

a Skin booster isn't about adding volume. It's about improving the quality of the skin itself.

That's why it works particularly well for dark circles caused by translucent skin,

where thinning skin allows underlying blood vessels to show through.

There's a wide range of options — Rejuran Eye, Juvelook, Redensyl, exosome-based products — but honestly,

the choice of product isn't the most important variable here.

Same Rejuran, But Why Does One Patient Swell for a Week While Another Looks Fine the Next Day?

Key Insight from Dr. Wi Young-jin

With under-eye Skin boosters, 'concentration control' matters far more than product selection.

Even with the same Rejuran, injecting it at standard concentration can cause Swelling that lasts 1–2 weeks,

whereas diluting it by 50% allows patients to look natural again from the very next day.

If you found this article by searching for under-eye Skin boosters,

you've probably come across conflicting reviews that left you confused.

One post says "I swelled up for a week after Rejuran Eye,"

while another says "I looked totally natural the next day."

Same product — so why such different outcomes?

Here's the thing: it's not a difference in product. It's a difference in concentration.

When Rejuran Eye is injected at its standard concentration (20mg/ml),

the PN molecules draw moisture into the Dermis,

and it's completely normal to look puffy for the first 1–2 weeks.

The under-eye skin is only about 0.5mm thick —

the thinnest area on the face — which makes this effect even more pronounced.

That's why, in my clinic, when treating the under-eye area,

I typically dilute the product 50% with normal saline before injecting.

Halving the PN concentration significantly reduces the initial fluid-drawing effect,

so most patients barely notice any difference by the next day.

To compensate, I simply add one additional session to achieve the same total dosage.

There's one important thing I need to be upfront about:

diluting the product naturally reduces the Collagen stimulation intensity per session.

So it does take a little longer to see full results.

That said, for patients who need to go back to work right after their procedure,

this approach is far more practical.

Key Summary from Dr. Wi Young-jin

In under-eye Skin boosters, "which product is used" accounts for about 30% of the outcome.

The remaining 70% comes down to concentration and injection depth.

Even with the same Rejuran Eye, 100% concentration and 50% diluted concentration should be considered two entirely different procedures.

Under-Eye Hollowing vs. Dark Circles — The Approach Differs Depending on Concentration and Procedure

I see this scenario so often that it deserves its own section.

Last week, a 38-year-old patient came in

saying she wanted to "fill in the under-eye hollowness with Rejuran Eye."

When I showed her with a mirror, she agreed —

but what she actually had wasn't dark circles. It was a deeply sunken tear trough.

A Skin booster simply cannot fill that kind of structural depression.

PN improves skin quality — it doesn't create volume.

So I declined the Skin booster that day,

and instead recommended starting conservatively with less than 1cc of tear trough Filler,

then following up with a Skin booster three months later to address any residual pigmentation.

If we had done it the other way around, the Filler would have been placed on top of Skin booster-induced edema,

leaving her with an unsettled, puffy appearance for an entire month.

So — which category do you fall into?

The Three Questions I Hear Most Often About Under-Eye Skin Boosters

Q1. How many sessions does it take to see results from an under-eye Skin booster?

A. The clinical data gives a fairly clear answer: 3–4 sessions is the standard recommendation.

That said, I see a few patients every week who say, "I just want to try one session before committing" —

and with diluted concentration, only about 2 out of 10 are satisfied after a single session.

The other 8 typically need 2–3 sessions before they personally notice a difference.

Photos show visible changes even after the first session,

but it's characteristic of this area that patients often can't perceive the improvement on their own.

And after hearing that, the next question almost always follows.

Q2. Each session adds up in cost — how long do the results actually last?

A. I used to think results lasted about a year, but based on actual follow-up data, 6–9 months is more realistic.

The under-eye area is where the orbicularis oculi muscle moves tens of thousands of times every single day.

That's why results in this area don't last as long as Skin boosters in other regions.

Most patients do an initial course of 3 sessions in the first year,

then come in for a single booster session every 6 months after that.

Before I wrap up, there's one more point that really matters.

Q3. How much Bruising or side effects should I expect?

A. I'll be honest — the answer is fairly predictable.

Bruising happens in almost every case.

The under-eye Dermis is laced with a network of tiny veins, and even with a cannula, we inevitably nick one or two.

That said, with precise placement, Bruising typically resolves within 3–5 days and can be covered with concealer.

The more serious concern is intravascular occlusion within the orbital area.

It's rare — occurring in roughly 0.05% of cases — but it's not zero.

That's why I exclusively use a cannula for all under-eye injections, without exception.

If there's one thing to take away from today — rather than asking which Skin booster to get, ask whether the concentration has been adjusted to match the thickness of your own under-eye skin.


In my next post, I'll cover whether you can have an under-eye Skin booster and tear trough Filler done on the same day. I'll walk through real cases showing how I decide in the clinic — who can get both at once and who needs to space them out. This has been Dr. Wi Young-jin.

Further Reading

• Hip Dips: Can Exercise Really Fill Them In? Why Squats Alone Won't Cut It

• Collagen Injections vs. Filler — What's Actually the Difference?

• Double Chin: Is It Fat or Lost Elasticity That's Really to Blame?