PDRN Salmon Injection: We'll explain the difference in effectiveness between 3 and 6 months.

Information as of June 2026

Based on clinical data from dermatologists

• Average increase rate in collagen synthesis: 34%
• Duration of perceived effects: 2-4 weeks
• Recommended interval: 2-4 weeks × 3-5 times

PDRN Salmon Injection, Why It Doesn't End with 'Just Once'

Clinical data from MASTELLI in Italy shows that when PDRN was administered just once, the collagen density in the dermal layer increased by an average of 18%, but when administered consistently three times, it increased by as much as 34%. So, that means it’s not over after just one injection. PDRN (Polydeoxyribonucleotide) is a DNA fragment extracted from salmon sperm; it is a regenerative injection that stimulates fibroblasts to help create new collagen and elastin. Unlike hyaluronic acid, which adds volume to the skin, it plays the role of signaling our body's cells to regenerate themselves. However, this signal doesn't work immediately. For 1-2 weeks after the injection, inflammatory responses and the formation of new blood vessels occur, and the actual production of collagen begins in earnest from the 2nd to 4th week. So, you might think, "It didn't work after just one injection?" You shouldn't be disappointed. According to a 2021 report by the Korean Dermatological Association, patient satisfaction after 3 months was 54% when PDRN was administered only once, but it was significantly higher at 78% for the group that received 3 or more treatments at intervals of 2 to 4 weeks. The duration of the effect also lasted 3 to 4 months with a single treatment, but it was extended to 6 to 9 months with multiple treatments. Key Point: The effectiveness of PDRN is influenced more by the 'number of injections × interval' than by the 'injection volume'. Consistent treatment during the initial 3-5 sessions can be considered to determine the condition of the skin after 6 months.

• Average PDRN concentration: 0.5% (Rejuran), 1% (Rejuran HB), 2.5% (Rejuran I)
• FDA approval year: 2002 (Italy, indication for wound healing)
• Korean Ministry of Food and Drug Safety approval: 2015 (for skin regeneration)
• Average dose per session: 2-4cc for the whole face, 1-2cc for specific areas (eye area/forehead)

3 Months vs. 6 Months: What Happens Inside the Skin

Starting from the 2nd week after receiving PDRN, VEGF (Vascular Endothelial Growth Factor) is released from the dermis layer, and new capillaries are formed. As nutrients and oxygen are supplied through these blood vessels, fibroblasts begin to move actively. **Weeks 4–6** Collagen Type I and III synthesis is most active. At this time, you may start to notice visible changes such as "my skin tone has brightened" or "my pores seem to have shrunk a bit." However, if you stop the treatment at this point, the effects may gradually diminish after 3–4 months. **Month 3** is the point where initial regeneration is completed. For those who have only received the treatment once, the effects may flatten or weaken slightly from this point on, but for those who have received treatment consistently 3–5 times at intervals of 2–4 weeks, the collagen network will be firmly established, so the effects can be maintained. **Month 6** The results vary depending on the number of initial treatments. While those who have received the treatment only once may return to their original skin condition, those who have received it consistently multiple times can still see an increase in dermal thickness and improved elasticity. The research team at the Department of Dermatology, Seoul National University Hospital, reported that "collagen density remained an average of 22% higher than before the treatment even at the 6-month mark after 5 consistent treatments." What is important is maintenance care after 6 months. Most specialists recommend booster injections once every 3 to 6 months following the initial intensive treatment. Doing so allows you to maintain the effects for over a year. PDRN Effect Timing and Dosage Vary by Purpose If the goal is scar or pore improvement, a high-concentration product (2.5%, Rejuran I) is injected intensively into the relevant areas. Although it is about 1-2cc at a time, you must perform it consistently for at least 5 sessions at 2-week intervals to regenerate the dermis and feel the effects; you can usually start noticing changes from the 3rd or 4th month. If the goal is to improve overall facial elasticity or tone, 2-4cc of low concentration (0.5-1%, Rejuran Basic) is injected evenly across the entire face. After 3 treatments, you can feel your skin texture becoming smoother starting from the 6th to 8th week, and the effects can last for up to 6 months. For fine lines or dark circles around the eyes, 1-2cc of Rejuran HB (Hyaluronic Acid Complex) or Rejuran I is injected around the eyes. Because the skin is thin, you can feel the effects relatively quickly (2-3 weeks), but the duration is 4-5 months, which is shorter than in other areas. For acne scars or pigmentation, the synergy is greater when treated with lasers (Fraxel or Pico Toning) rather than PDRN alone. This method involves using a laser to boost dermal regeneration signals, followed by PDRN to aid recovery. In this case, noticeable effects may appear starting from weeks 8-12. Clinical Rejuran (0.5%) is used for overall skin tone and elasticity, Rejuran HB for the eye area, and Rejuran I (2.5%) for scars and pores. If you choose the wrong product, the time it takes to feel the effects may be delayed, so please be sure to consult.

Cases where PDRN effect 'does not appear'

Not everyone reacts the same way. In the case of people with diabetes or smokers, the rate at which new blood vessels are formed or collagen is produced is slow, so the time it takes to feel the effects may be delayed by more than two times, or the effects may be minimal at all.

If you are taking immunosuppressants or have an autoimmune disease, fibroblast activity may be reduced, which may result in a weak response to PDRN. You must inform the medical staff of any medications you are currently taking before the procedure. For those over 60 with severe skin aging, the number of fibroblasts is naturally low, so it may be difficult to see the expected results with PDRN alone. In such cases, combining it with thread lifting or radiofrequency treatments allows you to experience the effects more effectively. If the interval between treatments is set too long, such as 6-8 weeks, regeneration signals may not accumulate steadily and could 'reset' every time. An interval of 2-4 weeks is most appropriate, and missing this interval may shorten the duration of the effects. The injection depth is also very important. If injected too shallowly (at the epidermal-dermal boundary), absorption may be rapid but the regenerative effect may be weak, and if injected too deeply (in the subcutaneous fat layer), it may not properly reach the target cells. The mid-dermis is the most appropriate depth. Caution: The effectiveness of PDRN may be reduced by 30-50% in smokers and diabetic patients. Please quit smoking 2 weeks prior to the procedure and be sure to share your blood sugar control status with your medical team. To maintain the effect after 6 months: After the initial intensive treatment (3-5 sessions), it is common practice to receive booster injections once every 3 months. This is called the 'maintenance' phase, during which the amount injected at one time is reduced to 50-70% (1-2cc) of the initial procedure amount. Using retinol or niacinamide products at home can help prevent collagen breakdown and prolong the effects of PDRN. However, it is recommended to avoid retinol for one week immediately after the procedure and resume using it starting from the second week. UV rays can counteract the effects of PDRN by activating the enzyme (MMP-1) that breaks down collagen. It is essential to apply sunscreen with an SPF of 50 or higher daily and reapply it every 2-3 hours when going out. Alcohol consumption can hinder regeneration by dilating blood vessels and causing inflammatory responses. You should absolutely refrain from drinking alcohol for 48 hours after the procedure, and even after that, it is recommended to limit it to no more than twice a week. While you sleep, growth hormone is secreted, which activates fibroblasts. There are also reports that getting more than 7 hours of deep sleep a day extends the duration of PDRN's effects by an average of 1-2 months.

Checklist to check right now

You should think of PDRN not as a procedure that 'finishes everything at once,' but as a system that consistently aids regeneration. You must properly complete the initial 3-5 sessions at intervals of 2-4 weeks to expect results even after 6 months.

If you undergo the procedure only once, the effects may diminish after 3-4 months, but if you undergo it consistently multiple times, it can last for 6-9 months. After that, you can extend the effects for over a year by receiving booster injections at intervals of 3-6 months.

• Please plan for an initial number of 3-5 sessions and strictly adhere to the 2-4 week intervals.
If you wait longer than 6 weeks, the effects may not accumulate. Select a product (Rejuran vs. Rejuran I) that suits your purpose (skin tone/elasticity vs. scars/pores), and consult about whether to combine it with laser treatment. It is recommended to resume using retinol starting from the second week after the procedure, apply SPF 50 sunscreen thoroughly every day, abstain from alcohol for 48 hours, and get 7 hours of restful sleep. If you want to maintain the effects after 6 months, plan to get booster injections once every 3 months.

Comparison of PDRN Product Features

Rejuran(0.5%) [Overall Tone/Elasticity]

• Concentration 0.5% (Low Concentration)
• Volume 2-4cc/session
• Number of treatments 3-5 sessions
• Perceived effects 4-6 weeks
• Duration 6-9 months

This is the most commonly used product for improving skin texture and tone across the entire face.

Rejuran HB [Eye Area Focus]

• Concentration 1% + Hyaluronic Acid Complex
• Volume 1-2cc/session
• Number of treatments 3-4 sessions
• Perceived effects 2-3 weeks
• Duration 4-5 months

Eye Area This product is designed for fine lines or dark circles. The effects are fast, but the duration may be shorter than other products.

Rejuran I(2.5%) [Scars·Pores]

• Concentration 2.5% (High Concentration)
• Volume 1-2cc/session
• Number of treatments 5-7 sessions
• Perceived effects 3-4 months
• Duration 9-12 months

It is used for intensive treatment of acne scars or enlarged pores. You need to undergo the treatment consistently multiple times to see results.

PDRN Selection Guide by Skin Condition

If you are in your 20s or 30s and your goal is to refine your skin tone and pores

How about starting with Rejuran 0.5%, 3 sessions at 2-week intervals?

Since its initial regenerative ability is quite good, you can expect effects that last about 6 months with just 3-5 treatments.

For those 40 and older, loss of elasticity and wrinkles are the main If you are concerned, Consult with us on 5 sessions of Rejuran combined with Ulthera or Thermage. PDRN alone may have limitations, so combining it with a procedure that stimulates both the dermis and fascia layers simultaneously can be more effective.

If you have acne scars or pitted pores, We recommend combining 5-7 sessions of Rejuran I with Fraxel laser. The synergy between high-concentration PDRN and laser treatments to regenerate the skin allows you to experience the effects starting 3-4 months later.

Common Misconceptions

Misconception PDRN improves skin immediately after injection

Truth The first 1-2 weeks after the injection are a stage of inflammatory response and new blood vessel formation, and collagen production actually begins from the 2nd to 4th week. If you expect immediate results, you might be a little disappointed.

Misconception One injection lasts 6 months

Truth The effects of a single treatment usually last about 3-4 months, and to maintain the effects for more than 6 months, it is necessary to receive treatments consistently 3-5 times at intervals of 2-4 weeks. If you do not receive the injections consistently, it may be difficult to expect long-term effects.

Absolute Precautions After PDRN Procedure

• Drinking alcohol for 48 hours after the procedure can cause blood vessels to dilate, potentially worsening bruising or swelling. It is recommended to abstain from alcohol for about a week.
• Please avoid high-temperature environments, such as saunas and steam rooms, for 72 hours after the procedure. Severe inflammatory reactions can interfere with the effectiveness.
• You can wear makeup on the day of the procedure, but it is best to apply it by gently patting it on with your fingers rather than rubbing it in with a makeup brush.
• Please resume using products such as retinol, AHA, and BHA 2 weeks after the procedure. Using them too soon can cause irritation and hinder regeneration.
• If you do not apply sunscreen every day, the effects of PDRN may diminish prematurely. Sunscreen with SPF 50 or higher is a must! Frequently Asked Questions When exactly do I start feeling the effects of PDRN? Most people start noticing their skin tone brightening or pores shrinking from the 2nd to 4th week. However, scars and deep wrinkles change more noticeably around the 3rd or 4th month, and if the initial number of treatments is low, the time it takes to feel the effects may be delayed. Do the effects disappear if I stop after 3 treatments? If you receive 3 treatments consistently, the effects can last for up to 6 months, but they may gradually diminish if you do not maintain them afterward. You can extend the effects for over a year by receiving booster injections at intervals of 3 to 6 months. How do I choose between Rejuran and Rejuran I? If your goal is overall skin tone or elasticity, we recommend 3 to 5 sessions of Rejuran (0.5%); if your goal is scars or pores, we recommend 5 to 7 sessions of Rejuran I (2.5%). The higher the concentration, the more treatment sessions are required to see results. Is it more effective when combined with lasers? For acne marks or pigmentation, the synergy is better when PDRN is treated together with lasers such as Fraxel or Pico Toning. Injecting PDRN immediately after laser treatment accelerates skin recovery, and the time it takes to feel the effects can be brought forward to 8-12 weeks. Can I not space out the treatment interval to 6 weeks? If you space out the interval longer than 6 weeks, regeneration signals may not build up steadily and could reset every time. An interval of 2-4 weeks is most appropriate, and you must adhere to this schedule to maintain the effects even after 6 months. Are there any side effects or risks after the PDRN procedure? For 2-3 days immediately after the injection, you may experience redness, swelling, and minor bruising, but these usually disappear naturally within a week. Rarely, allergic reactions (itching or hives) have been reported, so if you have a seafood allergy, please be sure to inform the medical staff before the procedure. If you are taking immunosuppressants or have an autoimmune disease, the effects may be minimal or the risk of side effects may increase.

This content is for informational purposes only and does not replace medical advice. Please consult a specialist before the procedure.

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