Rejuran Side Effects:
What to Expect After Treatment

The Common,
Expected Reactions

Redness, mild swelling, and small bruises at injection points are the most frequently reported effects, and they reflect the skin’s normal inflammatory response to microinjection rather than anything going wrong. These reactions are generally most visible in the first 24 hours and settle noticeably within a couple of days for most patients. For background on what the treatment is designed to do, see our Rejuran Healer overview.

Timeline for
Common Reactions

Reactions generally follow a predictable pattern, though individual healing speed varies.

Is Rejuran
Painful?

For most people, yes, and clinic pages tend to skip this part. A standard Rejuran Healer session places many small injections just under the surface of the skin across the treated area. Each one stings as the needle goes in and the liquid lifts a small bump.

Clinics almost always apply a numbing cream first, usually left on for around 30 minutes. It takes the edge off without removing the sensation. In a 2025 split-face trial of Rejuran published in the Journal of Cosmetic Dermatology, ten Korean volunteers had EMLA cream (lidocaine and prilocaine) on for 30 minutes and still rated needle injection at an average of 5.4 out of 10 for pain. The other half of the face, treated with a needle-free jet injector, averaged 2.9. Ten people is a very small sample, but that number is more honest than the phrase “mild discomfort”.

Some protocols go further. A 2024 Korean study of Rejuran for facial redness mixed a small amount of lidocaine into the injection and cooled the skin with medical CO2 gas after the numbing cream. If pain worries you, ask before booking how long the cream stays on, whether the product or mix contains lidocaine, and whether the clinic uses cooling. You would not be unusual in asking: in a 2026 survey of 501 Korean dermatologists, about a quarter named injection discomfort as a barrier to using polynucleotide injections.

The stinging stops soon after the session. Tenderness to touch can last a few days, as the timeline above shows. Pain that builds over the following days instead of fading is a different matter, and the next section covers it.

When a Reaction
Is Worth Flagging

Most reactions fall within the expected range described above and resolve on their own. The ones worth raising with a practitioner are those that break the pattern rather than those that simply feel uncomfortable: swelling that increases after the second day instead of settling, redness spreading beyond the injection points, an area that becomes hot, hard or increasingly tender, fever, or any reaction that appears days after the session rather than hours. None of those are common, and none of them are things to manage at home on the assumption that they are part of normal recovery.

For a broader look at what to expect from start to finish, our treatment process guide covers the full course, and our before and after guide addresses what results look like once side effects have resolved.

What the Published Data
Actually Reports

Clinic pages tend to describe side effects in adjectives. The clinical literature uses numbers, and they are worth knowing because they set a realistic expectation rather than a reassuring one.

A systematic review in the Journal of Cosmetic Dermatology (online December 2024, volume 24, 2025) pooled nine studies covering 219 patients treated with polynucleotide injections. None of the nine reported a severe adverse event. Two reported no side effects at all. Where effects were recorded they were local and transient: swelling in up to 71.4% of patients in the study reporting the highest rate, redness between roughly 3.7% and 10.7%, along with injection-site pain, itching and bruising. Most resolved within a week.

A separate 2026 retrospective study followed 23 patients through 91 sessions of intradermal polynucleotide treatment around the eye, with a minimum of 24 months of follow-up. Two mild events occurred across those 91 sessions (one transient swelling and one case of injectable papules persisting up to 24 hours), which works out to 2.2% of sessions. The authors recorded no moderate or severe events and, specifically, no delayed ones, which is the question repeat treatment usually raises.

Two caveats belong with those figures. The pooled review covers 219 patients in total, which is small, and the authors say plainly that the studies were heterogeneous enough to prevent a meta-analysis. And the products studied are polynucleotide injectables as a class, not Rejuran specifically.

The Rare Complication
Worth Knowing About

Serious complications after polynucleotide injection are rare, but they are not hypothetical, and a page about side effects that omits them is not being straight with you.

A 2026 case report in the same journal describes an otherwise healthy 57-year-old woman who developed bilateral cheek abscesses after polynucleotide injections. Symptoms started within 24 hours and progressed over five days into fluctuant masses that needed imaging and surgical drainage on day six. The organisms cultured were gram-negative, which matters because the first antibiotic used targeted gram-positive bacteria and did not work. The infection resolved, but at six months she had atrophic scarring on both cheeks with visible contour depression.

The practical lesson is about escalation rather than avoidance. Swelling that keeps worsening after the first day or two, becomes fluctuant or tender, or fails to respond to an initial antibiotic is not a normal reaction running long. That is the point to get back in front of a clinician rather than waiting it out, and the authors of the case report make exactly that argument about early imaging and culture.

Frequently Asked
Questions

Why does Rejuran hurt more than some other injections?

Each session involves many separate needle entries close to the skin surface, and each one raises a small bump of liquid. Numbing cream reduces the sting but does not remove it. In one small trial, people still rated the injections about 5 out of 10 for pain after 30 minutes of cream.

Is bruising normal after Rejuran?

Small bruises at injection points are a common and expected reaction to microinjection, similar to what you might see after a blood draw, and typically fade within a week.

How can I reduce swelling after treatment?

Avoiding strenuous activity and alcohol for the rest of the day, and following any specific aftercare instructions from your practitioner, generally helps minimize swelling.

Can I apply makeup over the treated area right after?

Most practitioners recommend waiting several hours to a full day to reduce irritation risk at fresh injection points.

Are allergic reactions to Rejuran common?

They’re uncommon given the biocompatible nature of the polynucleotide formulation, but anyone with known fish allergies should discuss this specifically with a practitioner beforehand.

When should I contact my provider about a reaction?

Reach out if swelling or redness worsens after the first couple of days, or if you notice signs of infection like increasing warmth, pus, or fever.

How long does bruising actually last?

Longer than the other effects. Puncture marks generally settle within a day and the small raised bumps flatten over one to three days, but a bruise can take up to about a week to fade, and it is more likely around the eyes and in anyone taking blood thinners or fish oil. If you are in Korea for a short trip, that is the reason to book early in it rather than the day before something that matters.

Is redness the same thing as a reaction?

No, and the distinction is the useful part. Redness at the injection points on the day is the expected response to dozens of needle entries. A reaction worth reporting is one that breaks the pattern: increasing after the second day, spreading beyond the injection sites, becoming hot or hard, or appearing days later rather than hours.