The Niacinamide 15 Serum
A highly concentrated K-beauty serum delivering 15% niacinamide alongside Zinc PCA and Acetyl Glucosamine to visibly refine pores, regulate sebum, fade post-acne marks, and smooth uneven skin texture β clinically tested to reduce excess oil by up to 50% in just 4 weeks.
β¨ Texture & Feel
Clinically Proven Sebum Control
Independently tested and shown to reduce excess oil by up to 50% and decrease pore appearance by 45% after 4 weeks of consistent use.
Fades Post-Acne Marks
The 15% niacinamide + 2% Acetyl Glucosamine (NAG) synergy delivers a clinical 19% improvement in pigmentation and 15% reduction in visible blemishes.
Barrier-Strengthening Formula
Niacinamide boosts ceramide synthesis for a stronger, healthier moisture barrier while Allantoin soothes irritation and supports collagen renewal.
Lightweight, Non-Sticky Texture
Formulated without silicones, oils or heavy occlusives β absorbs instantly without residue, making it ideal layered under moisturizer or SPF.
Minimal, Clean Ingredient List
Only 15 thoughtfully chosen ingredients β free from fragrance, parabens, sulfates, mineral oil, artificial colors and harsh alcohols.
Zinc PCA Duo Action
Zinc PCA (1%) works alongside niacinamide to inhibit acne-causing bacteria, reduce inflammation and limit sebum secretion from the source.
π‘οΈ Safety & Compatibility
Niacinamide (Vitamin B3) is widely considered safe during pregnancy and breastfeeding. The formula contains no retinoids, salicylic acid, hydroquinone or chemical sunscreens. Always consult your healthcare provider.
Contains no fermented ingredients, fatty acids, esters, or polysorbates that are known to feed Malassezia yeast. This formula is considered safe for fungal acne-prone skin.
Independently tested and confirmed non-comedogenic. Contains no pore-clogging oils, waxes or heavy emollients. Suitable for congested or breakout-prone skin.
Zero added fragrance, artificial colorants or common allergens. Dermatologist-tested formula with a low irritation potential β suitable for most sensitive skin types.
At 15% niacinamide, this is a high-potency formula. A small percentage of users may experience initial flushing, dryness or sensitivity. Perform a patch test and introduce gradually if new to niacinamide serums.
Avoid applying simultaneously with AHA/BHA, Vitamin C or Retinol in the same routine step β these combinations can be overstimulating. Safe to use alongside hyaluronic acid, peptides and moisturizing ingredients.
π¬ Ingredient Breakdown
β Niacinamide 15% Proven
The hero active at a high 15% concentration. Niacinamide (Vitamin B3) is one of the most well-researched multitasking skincare ingredients. At this concentration it visibly controls sebum, refines enlarged pores, fades hyperpigmentation, reduces redness and strengthens the skin barrier by boosting ceramide synthesis.
- Sebum Regulation: Clinically shown to reduce oiliness by 48% in 4 weeks (Dermacosmetic Skin Science Laboratory).
- Pore Minimizing: 45% reduction in visible pore size after 4 weeks in clinical testing.
- Brightening: Inhibits melanosome transfer to keratinocytes, effectively fading dark spots and post-acne marks.
- Barrier Repair: Stimulates ceramide, fatty acid and cholesterol production for a stronger moisture barrier.
- Anti-Inflammatory: Reduces redness, calms active breakouts and soothes atopic or rosacea-affected skin.
πΏ Acetyl Glucosamine (NAG) 2% Proven
An amino sugar naturally found in the skin that works synergistically with niacinamide. It promotes hyaluronic acid production for deeper hydration, provides antioxidant protection, exfoliates dead skin cells and is clinically shown to be more effective at reducing hyperpigmentation when paired with niacinamide than either ingredient alone.
- Brightening Synergy: Clinical double-blind trials show the niacinamide + NAG duo is significantly more effective at fading brown spots than niacinamide alone.
- Hydration Boost: Stimulates hyaluronic acid synthesis within the skin, improving moisture retention over time.
- Mild Exfoliation: Gently smooths rough texture and refines skin surface without photosensitizing side effects.
π΅ Zinc PCA 1% Proven
A synergistic combination of zinc and L-PCA (pyrrolidone carboxylic acid). Zinc PCA reduces sebum secretion from sebaceous glands, inhibits the proliferation of acne-causing bacteria (C. acnes), calms inflammation and has humectant properties that keep skin hydrated without greasiness.
- Anti-Bacterial: Limits the growth of Cutibacterium acnes, the primary bacteria responsible for inflammatory acne.
- Sebostatic Action: Reduces sebum output at the gland level, complementing niacinamide's oil-regulating effects for a combined reduction of up to 50%.
- Humectant: The PCA component attracts water to the skin's upper layers, keeping the formula balanced and non-dehydrating.
πΈ Allantoin 0.1% Proven
A classic skin-soothing ingredient derived from comfrey root (now synthetically produced for purity). At 0.1%, allantoin moisturizes, calms irritation, promotes cell regeneration and collagen synthesis, helping the skin recover more quickly from breakouts and minimizing post-acne scarring.
- Soothing: Reduces transepidermal water loss and calms reactive or inflamed skin.
- Wound Healing: Promotes cell proliferation and collagen formation to speed recovery from blemishes.
- Safety Profile: Well-tolerated even by sensitive skin at the concentrations used in cosmetics.
π Tocopherol (Vitamin E) trace Promising
A fat-soluble antioxidant that protects skin cells from free radical damage caused by UV and pollution. In this formula, tocopherol also helps stabilize the niacinamide and extends the product's shelf life by preventing oxidation of other ingredients.
- Antioxidant Defense: Neutralizes free radicals, helping prevent premature signs of aging from environmental stressors.
- Formulation Stability: Acts as a natural preservative co-ingredient, protecting the formula's potency over time.
15 ingredients
Water, Pentylene Glycol, Niacinamide (15%), Butylene Glycol, Acetyl Glucosamine (2%), 1,2-Hexanediol, Zinc PCA (1%), Trehalose, Xanthan Gum, Pullulan, Allantoin (0.1%), Ethylhexylglycerin, Sodium Phytate, Citric Acid, Tocopherol
π Where It Fits in Your Routine
Apply after toner, before moisturizer. Can be used AM and PM. Always follow with SPF 30+ in the morning. Do not layer directly with Vitamin C (L-ascorbic acid) or AHA/BHA in the same step.
π How to Use
Cleanse & Tone
Begin with a gentle cleanser to remove makeup, sunscreen and excess oil. Follow with your preferred toner or essence to prep skin and balance pH before applying actives.
Dispense 3β4 Drops
Tilt the dropper bottle and dispense 3β4 drops (approximately a pea-sized amount) onto clean fingertips or directly into the palm of your hand.
Apply to Face & Neck
Starting from the center of your face, gently press and massage the serum outward toward the hairline and jawline. Can also be applied to the neck and dΓ©colletage. Avoid direct eye contact.
Pat to Absorb
Gently pat (do not rub) the serum into the skin using fingertip pressure until fully absorbed β typically in under 30 seconds thanks to the lightweight, watery texture.
Moisturize & Protect
Follow with your moisturizer to seal in the serum and support the skin barrier. In the morning, always finish with a broad-spectrum SPF 30+ sunscreen to protect brightening results.
π€ Who Is It For?
β Perfect for you if:
- You struggle with excess oil, shine or enlarged pores
- You have persistent or recurring acne breakouts
- You want to fade post-acne dark spots and redness
- You prefer minimal, fragrance-free formulas
- You have oily, combination, or blemish-prone skin
- You want clinically-backed results at an affordable price
- You are pregnant or breastfeeding and need a safe active serum
β Consider alternatives if:
- You have never used niacinamide before (start at 5β10%)
- Your skin is extremely reactive or barrier-compromised
- You primarily need deep hydration (pair with a richer moisturizer)
- You are looking for a retinol or exfoliant alternative
- You want anti-aging as the primary focus (niacinamide helps but peptides are stronger)
π― Skin Type Compatibility
Ideal fit. Clinically reduces sebum by up to 50% in 4 weeks. Lightweight, non-sticky formula absorbs instantly without adding greasiness or shine.
Balances oily T-zone without over-drying drier cheek areas. The humectant ingredients (trehalose, zinc PCA) keep skin comfortable across zones.
Non-comedogenic, fungal-acne safe formula. Niacinamide + Zinc PCA target active breakouts, calm inflammation and visibly reduce blemish marks over time.
Provides hydration via trehalose and acetyl glucosamine but may feel insufficient alone on very dry skin. Pair with a richer, occlusive moisturizer for best results.
Fragrance-free and allantoin-soothed formula is gentle in principle. However, 15% niacinamide is a high concentration β strongly recommended to patch test and introduce slowly every other evening.
π Results Timeline
Improved Skin Texture & Reduced Shine
Most users report noticeably less oil and shine within the first week. Skin begins to feel smoother and more balanced. Some users new to high-concentration niacinamide may experience minor initial dryness or tingling β this typically resolves within days.
~70% noticed within Week 1Visible Pore Reduction & Calmer Breakouts
Clinical data shows a 45% decrease in pore size and 48% reduction in oiliness by the 4-week mark. Active breakouts begin to calm, and the frequency of new blemishes starts to decrease. Early fading of lighter post-acne marks begins.
45% pore reduction β clinical dataPost-Acne Marks Visibly Fading
The niacinamide + acetyl glucosamine synergy delivers a clinical 19% improvement in pigmentation. Darker post-acne marks, redness and uneven tone become noticeably more even. Skin texture is smoother and more refined overall.
19% pigmentation improvement β clinical dataClearer, More Balanced Complexion
Continued use solidifies barrier strength, long-term sebum regulation and hyperpigmentation fading. Users report significantly fewer breakouts, more even skin tone and a naturally matte but healthy appearance with less need for heavy coverage makeup.
~85% report overall complexion improvementβ Ratings by Platform
βοΈ Pros & Cons
β Praised
- Clinically proven sebum reduction (up to 50% in 4 weeks)
- Visibly minimizes pore size with continued use
- Fades post-acne marks and redness effectively
- Extremely clean, minimal ingredient list (15 ingredients)
- Lightweight, fast-absorbing and non-sticky texture
- Completely fragrance-free β no scent whatsoever
- Fungal acne safe and non-comedogenic tested
- Pregnancy-safe formula with no contraindicated actives
- Very affordable price point for a 15% niacinamide serum
β Criticized
- Small 20ml bottle β doesn't last long with daily use
- Thick glass bottle makes it difficult to gauge remaining product
- Dropper packaging can be prone to spillage during travel
- High 15% concentration not ideal for beginners or very sensitive skin
- May need a richer moisturizer for dry skin types
- Results for deep, stubborn hyperpigmentation take 8+ weeks
π° Budget-Friendly Alternatives (Dupes)
Similar zinc PCA pairing but at a lower 10% niacinamide concentration. Equally lightweight, fragrance-free and non-comedogenic. Lacks Acetyl Glucosamine for brightening synergy but is an excellent entry-level option for first-time niacinamide users.
Transparent formulation philosophy similar to COSRX. 10% niacinamide is effective but milder. Suitable for those who found 15% too potent. No Acetyl Glucosamine, slightly simpler ingredient profile but highly praised for tolerability.
Higher price point with 10% niacinamide + acetyl glucosamine similar to COSRX but at lower concentrations. Formulated as a customizable booster to mix into other products. Excellent tolerability but significantly more expensive for similar actives at lower doses.
π Comparison with Competitors
COSRX The Niacinamide 15 Serum β Featured
~$14β$25The Ordinary Niacinamide 10% + Zinc 1%
~$5.90Medicube Pore & Oil Control Serum (Niacinamide 10%)
~$20β$28Paula's Choice 10% Niacinamide Booster
~$44π¦ Storage & Shelf Life
12 months after opening. Use within 12 months of first opening for optimal potency and safety. Check the PAO symbol (open jar icon) on your packaging.
Store in a cool, dry place away from direct sunlight and heat. Avoid storing in humid environments like bathrooms when possible β a bedroom vanity or cabinet is ideal to preserve niacinamide stability.
Opaque dark glass dropper bottle with a precision pipette. The dark glass protects niacinamide from light degradation. Note: the thick glass walls mean the bottle looks fuller than it is β hard to gauge remaining product visually.
At 20ml (0.67 fl oz), this is well within the 100ml airline carry-on liquid limit. However, the dropper cap is not spill-proof β wrap securely or pack in a sealed bag when traveling to avoid leaks.
β Frequently Asked Questions
Yes β COSRX The Niacinamide 15 Serum is considered safe for use during pregnancy and breastfeeding. Niacinamide (Vitamin B3) is a well-tolerated water-soluble vitamin with no known contraindications during pregnancy. The formula contains no retinoids, salicylic acid, hydroquinone, benzoyl peroxide, or chemical sunscreens β all of which are typically avoided during pregnancy. As always, it is recommended to consult your OB/GYN or dermatologist before adding any new skincare active during pregnancy.
Yes β this serum is considered fungal acne (malassezia folliculitis) safe. The formula contains no fermented ingredients, fatty acid esters (such as isocetyl stearate or polysorbates), or other ingredients known to feed Malassezia yeast. The 15 total ingredients are all minimal and well-screened. Niacinamide, Zinc PCA and Acetyl Glucosamine can actually help manage fungal acne-related oiliness and inflammation. This makes it a great choice for those dealing with both fungal acne and regular inflammatory acne.
Niacinamide can be used alongside most actives but timing matters. Avoid applying it in the same routine step as high-potency Vitamin C (L-ascorbic acid) as this combination can cause temporary yellowing or reduce the stability of both ingredients β use them at different times of day instead (e.g. Vitamin C in the AM, niacinamide in the PM). With retinol, AHA and BHA, simply apply them separately (use niacinamide first as a serum, then retinol or exfoliants later, or alternate evenings). Niacinamide actually pairs synergistically with hyaluronic acid, peptides and ceramide-based products.
This serum is ideally suited for oily, combination, and acne-prone skin types. The clinically tested sebum-reducing and pore-refining benefits are most impactful for those who struggle with excess oil and enlarged pores. It is also excellent for skin with post-acne hyperpigmentation, uneven tone or texture. While dry and sensitive skin types can use it, the high 15% concentration means it should be introduced gradually β every other day initially β and always followed by a rich moisturizer. It is not the best choice as a standalone hydrator for dry skin but pairs well with a hydrating serum or cream.
Most users notice reduced oiliness and a more matte finish within the first 1β2 weeks. Clinical testing by the Dermacosmetic Skin Science Laboratory shows a 45% decrease in visible pore size and 48% reduction in oiliness by 4 weeks of consistent daily use. For post-acne marks and hyperpigmentation, expect visible improvement between 4 and 8 weeks, with significant results by week 12. Consistency is key β use it daily (AM and/or PM) for best results and always protect with SPF in the daytime to prevent new pigmentation from forming.
Apply The Niacinamide 15 Serum after cleansing and toning, in the serum step β before your moisturizer. As a water-based, lightweight serum it should go on before heavier, oil-based products or creams. The routine order is: Cleanser β Toner/Essence β Niacinamide Serum β Moisturizer β SPF (morning only). It can be used both morning and evening. If using other active serums (vitamin C, retinol, exfoliants), apply niacinamide first or use them in separate AM/PM routines.
No β COSRX The Niacinamide 15 Serum has been independently tested and certified non-comedogenic (comedogenic rating: 0/5). It contains no oils, waxes, heavy silicones or known pore-clogging ingredients. Niacinamide itself is actually anti-comedogenic and helps reduce the sebum buildup inside pores that leads to blackheads and whiteheads. This serum is safe for acne-prone, congested and oily skin without risk of triggering breakouts from the formula itself.
The Period After Opening (PAO) for COSRX The Niacinamide 15 Serum is 12 months. Once opened, use within 12 months for full potency and safety. At a typical usage of 3β4 drops once or twice daily, the 20ml bottle will last approximately 3β5 weeks with daily use, or up to 6β8 weeks if used once daily on the face only. Store in a cool, dry place away from direct sunlight to preserve the stability of niacinamide throughout this period.
Verdict: COSRX The Niacinamide 15 Serum stands out as one of the most potent and cleanest niacinamide serums available at its price point. The clinically-backed 15% niacinamide + 1% Zinc PCA + 2% Acetyl Glucosamine trio delivers genuine, measurable results β including a documented 45% reduction in pore appearance and up to 50% less sebum in 4 weeks. With only 15 ingredients, zero fragrance, fungal-acne-safe status and a pregnancy-safe profile, it checks nearly every box for oily, acne-prone and combination skin types. The main caveats are the small 20ml bottle size and the high concentration which requires a gradual introduction for sensitive skin. For the price, this is exceptional K-beauty value.
Product Information
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Description
A highly concentrated K-beauty serum delivering 15% niacinamide alongside Zinc PCA and Acetyl Glucosamine to visibly refine pores, regulate sebum, fade post-acne marks, and smooth uneven skin texture β clinically tested to reduce excess oil by up to 50% in just 4 weeks.
β¨ Texture & Feel
Clinically Proven Sebum Control
Independently tested and shown to reduce excess oil by up to 50% and decrease pore appearance by 45% after 4 weeks of consistent use.
Fades Post-Acne Marks
The 15% niacinamide + 2% Acetyl Glucosamine (NAG) synergy delivers a clinical 19% improvement in pigmentation and 15% reduction in visible blemishes.
Barrier-Strengthening Formula
Niacinamide boosts ceramide synthesis for a stronger, healthier moisture barrier while Allantoin soothes irritation and supports collagen renewal.
Lightweight, Non-Sticky Texture
Formulated without silicones, oils or heavy occlusives β absorbs instantly without residue, making it ideal layered under moisturizer or SPF.
Minimal, Clean Ingredient List
Only 15 thoughtfully chosen ingredients β free from fragrance, parabens, sulfates, mineral oil, artificial colors and harsh alcohols.
Zinc PCA Duo Action
Zinc PCA (1%) works alongside niacinamide to inhibit acne-causing bacteria, reduce inflammation and limit sebum secretion from the source.
π‘οΈ Safety & Compatibility
Niacinamide (Vitamin B3) is widely considered safe during pregnancy and breastfeeding. The formula contains no retinoids, salicylic acid, hydroquinone or chemical sunscreens. Always consult your healthcare provider.
Contains no fermented ingredients, fatty acids, esters, or polysorbates that are known to feed Malassezia yeast. This formula is considered safe for fungal acne-prone skin.
Independently tested and confirmed non-comedogenic. Contains no pore-clogging oils, waxes or heavy emollients. Suitable for congested or breakout-prone skin.
Zero added fragrance, artificial colorants or common allergens. Dermatologist-tested formula with a low irritation potential β suitable for most sensitive skin types.
At 15% niacinamide, this is a high-potency formula. A small percentage of users may experience initial flushing, dryness or sensitivity. Perform a patch test and introduce gradually if new to niacinamide serums.
Avoid applying simultaneously with AHA/BHA, Vitamin C or Retinol in the same routine step β these combinations can be overstimulating. Safe to use alongside hyaluronic acid, peptides and moisturizing ingredients.
π¬ Ingredient Breakdown
β Niacinamide 15% Proven
The hero active at a high 15% concentration. Niacinamide (Vitamin B3) is one of the most well-researched multitasking skincare ingredients. At this concentration it visibly controls sebum, refines enlarged pores, fades hyperpigmentation, reduces redness and strengthens the skin barrier by boosting ceramide synthesis.
- Sebum Regulation: Clinically shown to reduce oiliness by 48% in 4 weeks (Dermacosmetic Skin Science Laboratory).
- Pore Minimizing: 45% reduction in visible pore size after 4 weeks in clinical testing.
- Brightening: Inhibits melanosome transfer to keratinocytes, effectively fading dark spots and post-acne marks.
- Barrier Repair: Stimulates ceramide, fatty acid and cholesterol production for a stronger moisture barrier.
- Anti-Inflammatory: Reduces redness, calms active breakouts and soothes atopic or rosacea-affected skin.
πΏ Acetyl Glucosamine (NAG) 2% Proven
An amino sugar naturally found in the skin that works synergistically with niacinamide. It promotes hyaluronic acid production for deeper hydration, provides antioxidant protection, exfoliates dead skin cells and is clinically shown to be more effective at reducing hyperpigmentation when paired with niacinamide than either ingredient alone.
- Brightening Synergy: Clinical double-blind trials show the niacinamide + NAG duo is significantly more effective at fading brown spots than niacinamide alone.
- Hydration Boost: Stimulates hyaluronic acid synthesis within the skin, improving moisture retention over time.
- Mild Exfoliation: Gently smooths rough texture and refines skin surface without photosensitizing side effects.
π΅ Zinc PCA 1% Proven
A synergistic combination of zinc and L-PCA (pyrrolidone carboxylic acid). Zinc PCA reduces sebum secretion from sebaceous glands, inhibits the proliferation of acne-causing bacteria (C. acnes), calms inflammation and has humectant properties that keep skin hydrated without greasiness.
- Anti-Bacterial: Limits the growth of Cutibacterium acnes, the primary bacteria responsible for inflammatory acne.
- Sebostatic Action: Reduces sebum output at the gland level, complementing niacinamide's oil-regulating effects for a combined reduction of up to 50%.
- Humectant: The PCA component attracts water to the skin's upper layers, keeping the formula balanced and non-dehydrating.
πΈ Allantoin 0.1% Proven
A classic skin-soothing ingredient derived from comfrey root (now synthetically produced for purity). At 0.1%, allantoin moisturizes, calms irritation, promotes cell regeneration and collagen synthesis, helping the skin recover more quickly from breakouts and minimizing post-acne scarring.
- Soothing: Reduces transepidermal water loss and calms reactive or inflamed skin.
- Wound Healing: Promotes cell proliferation and collagen formation to speed recovery from blemishes.
- Safety Profile: Well-tolerated even by sensitive skin at the concentrations used in cosmetics.
π Tocopherol (Vitamin E) trace Promising
A fat-soluble antioxidant that protects skin cells from free radical damage caused by UV and pollution. In this formula, tocopherol also helps stabilize the niacinamide and extends the product's shelf life by preventing oxidation of other ingredients.
- Antioxidant Defense: Neutralizes free radicals, helping prevent premature signs of aging from environmental stressors.
- Formulation Stability: Acts as a natural preservative co-ingredient, protecting the formula's potency over time.
15 ingredients
Water, Pentylene Glycol, Niacinamide (15%), Butylene Glycol, Acetyl Glucosamine (2%), 1,2-Hexanediol, Zinc PCA (1%), Trehalose, Xanthan Gum, Pullulan, Allantoin (0.1%), Ethylhexylglycerin, Sodium Phytate, Citric Acid, Tocopherol
π Where It Fits in Your Routine
Apply after toner, before moisturizer. Can be used AM and PM. Always follow with SPF 30+ in the morning. Do not layer directly with Vitamin C (L-ascorbic acid) or AHA/BHA in the same step.
π How to Use
Cleanse & Tone
Begin with a gentle cleanser to remove makeup, sunscreen and excess oil. Follow with your preferred toner or essence to prep skin and balance pH before applying actives.
Dispense 3β4 Drops
Tilt the dropper bottle and dispense 3β4 drops (approximately a pea-sized amount) onto clean fingertips or directly into the palm of your hand.
Apply to Face & Neck
Starting from the center of your face, gently press and massage the serum outward toward the hairline and jawline. Can also be applied to the neck and dΓ©colletage. Avoid direct eye contact.
Pat to Absorb
Gently pat (do not rub) the serum into the skin using fingertip pressure until fully absorbed β typically in under 30 seconds thanks to the lightweight, watery texture.
Moisturize & Protect
Follow with your moisturizer to seal in the serum and support the skin barrier. In the morning, always finish with a broad-spectrum SPF 30+ sunscreen to protect brightening results.
π€ Who Is It For?
β Perfect for you if:
- You struggle with excess oil, shine or enlarged pores
- You have persistent or recurring acne breakouts
- You want to fade post-acne dark spots and redness
- You prefer minimal, fragrance-free formulas
- You have oily, combination, or blemish-prone skin
- You want clinically-backed results at an affordable price
- You are pregnant or breastfeeding and need a safe active serum
β Consider alternatives if:
- You have never used niacinamide before (start at 5β10%)
- Your skin is extremely reactive or barrier-compromised
- You primarily need deep hydration (pair with a richer moisturizer)
- You are looking for a retinol or exfoliant alternative
- You want anti-aging as the primary focus (niacinamide helps but peptides are stronger)
π― Skin Type Compatibility
Ideal fit. Clinically reduces sebum by up to 50% in 4 weeks. Lightweight, non-sticky formula absorbs instantly without adding greasiness or shine.
Balances oily T-zone without over-drying drier cheek areas. The humectant ingredients (trehalose, zinc PCA) keep skin comfortable across zones.
Non-comedogenic, fungal-acne safe formula. Niacinamide + Zinc PCA target active breakouts, calm inflammation and visibly reduce blemish marks over time.
Provides hydration via trehalose and acetyl glucosamine but may feel insufficient alone on very dry skin. Pair with a richer, occlusive moisturizer for best results.
Fragrance-free and allantoin-soothed formula is gentle in principle. However, 15% niacinamide is a high concentration β strongly recommended to patch test and introduce slowly every other evening.
π Results Timeline
Improved Skin Texture & Reduced Shine
Most users report noticeably less oil and shine within the first week. Skin begins to feel smoother and more balanced. Some users new to high-concentration niacinamide may experience minor initial dryness or tingling β this typically resolves within days.
~70% noticed within Week 1Visible Pore Reduction & Calmer Breakouts
Clinical data shows a 45% decrease in pore size and 48% reduction in oiliness by the 4-week mark. Active breakouts begin to calm, and the frequency of new blemishes starts to decrease. Early fading of lighter post-acne marks begins.
45% pore reduction β clinical dataPost-Acne Marks Visibly Fading
The niacinamide + acetyl glucosamine synergy delivers a clinical 19% improvement in pigmentation. Darker post-acne marks, redness and uneven tone become noticeably more even. Skin texture is smoother and more refined overall.
19% pigmentation improvement β clinical dataClearer, More Balanced Complexion
Continued use solidifies barrier strength, long-term sebum regulation and hyperpigmentation fading. Users report significantly fewer breakouts, more even skin tone and a naturally matte but healthy appearance with less need for heavy coverage makeup.
~85% report overall complexion improvementβ Ratings by Platform
βοΈ Pros & Cons
β Praised
- Clinically proven sebum reduction (up to 50% in 4 weeks)
- Visibly minimizes pore size with continued use
- Fades post-acne marks and redness effectively
- Extremely clean, minimal ingredient list (15 ingredients)
- Lightweight, fast-absorbing and non-sticky texture
- Completely fragrance-free β no scent whatsoever
- Fungal acne safe and non-comedogenic tested
- Pregnancy-safe formula with no contraindicated actives
- Very affordable price point for a 15% niacinamide serum
β Criticized
- Small 20ml bottle β doesn't last long with daily use
- Thick glass bottle makes it difficult to gauge remaining product
- Dropper packaging can be prone to spillage during travel
- High 15% concentration not ideal for beginners or very sensitive skin
- May need a richer moisturizer for dry skin types
- Results for deep, stubborn hyperpigmentation take 8+ weeks
π° Budget-Friendly Alternatives (Dupes)
Similar zinc PCA pairing but at a lower 10% niacinamide concentration. Equally lightweight, fragrance-free and non-comedogenic. Lacks Acetyl Glucosamine for brightening synergy but is an excellent entry-level option for first-time niacinamide users.
Transparent formulation philosophy similar to COSRX. 10% niacinamide is effective but milder. Suitable for those who found 15% too potent. No Acetyl Glucosamine, slightly simpler ingredient profile but highly praised for tolerability.
Higher price point with 10% niacinamide + acetyl glucosamine similar to COSRX but at lower concentrations. Formulated as a customizable booster to mix into other products. Excellent tolerability but significantly more expensive for similar actives at lower doses.
π Comparison with Competitors
COSRX The Niacinamide 15 Serum β Featured
~$14β$25The Ordinary Niacinamide 10% + Zinc 1%
~$5.90Medicube Pore & Oil Control Serum (Niacinamide 10%)
~$20β$28Paula's Choice 10% Niacinamide Booster
~$44π¦ Storage & Shelf Life
12 months after opening. Use within 12 months of first opening for optimal potency and safety. Check the PAO symbol (open jar icon) on your packaging.
Store in a cool, dry place away from direct sunlight and heat. Avoid storing in humid environments like bathrooms when possible β a bedroom vanity or cabinet is ideal to preserve niacinamide stability.
Opaque dark glass dropper bottle with a precision pipette. The dark glass protects niacinamide from light degradation. Note: the thick glass walls mean the bottle looks fuller than it is β hard to gauge remaining product visually.
At 20ml (0.67 fl oz), this is well within the 100ml airline carry-on liquid limit. However, the dropper cap is not spill-proof β wrap securely or pack in a sealed bag when traveling to avoid leaks.
β Frequently Asked Questions
Yes β COSRX The Niacinamide 15 Serum is considered safe for use during pregnancy and breastfeeding. Niacinamide (Vitamin B3) is a well-tolerated water-soluble vitamin with no known contraindications during pregnancy. The formula contains no retinoids, salicylic acid, hydroquinone, benzoyl peroxide, or chemical sunscreens β all of which are typically avoided during pregnancy. As always, it is recommended to consult your OB/GYN or dermatologist before adding any new skincare active during pregnancy.
Yes β this serum is considered fungal acne (malassezia folliculitis) safe. The formula contains no fermented ingredients, fatty acid esters (such as isocetyl stearate or polysorbates), or other ingredients known to feed Malassezia yeast. The 15 total ingredients are all minimal and well-screened. Niacinamide, Zinc PCA and Acetyl Glucosamine can actually help manage fungal acne-related oiliness and inflammation. This makes it a great choice for those dealing with both fungal acne and regular inflammatory acne.
Niacinamide can be used alongside most actives but timing matters. Avoid applying it in the same routine step as high-potency Vitamin C (L-ascorbic acid) as this combination can cause temporary yellowing or reduce the stability of both ingredients β use them at different times of day instead (e.g. Vitamin C in the AM, niacinamide in the PM). With retinol, AHA and BHA, simply apply them separately (use niacinamide first as a serum, then retinol or exfoliants later, or alternate evenings). Niacinamide actually pairs synergistically with hyaluronic acid, peptides and ceramide-based products.
This serum is ideally suited for oily, combination, and acne-prone skin types. The clinically tested sebum-reducing and pore-refining benefits are most impactful for those who struggle with excess oil and enlarged pores. It is also excellent for skin with post-acne hyperpigmentation, uneven tone or texture. While dry and sensitive skin types can use it, the high 15% concentration means it should be introduced gradually β every other day initially β and always followed by a rich moisturizer. It is not the best choice as a standalone hydrator for dry skin but pairs well with a hydrating serum or cream.
Most users notice reduced oiliness and a more matte finish within the first 1β2 weeks. Clinical testing by the Dermacosmetic Skin Science Laboratory shows a 45% decrease in visible pore size and 48% reduction in oiliness by 4 weeks of consistent daily use. For post-acne marks and hyperpigmentation, expect visible improvement between 4 and 8 weeks, with significant results by week 12. Consistency is key β use it daily (AM and/or PM) for best results and always protect with SPF in the daytime to prevent new pigmentation from forming.
Apply The Niacinamide 15 Serum after cleansing and toning, in the serum step β before your moisturizer. As a water-based, lightweight serum it should go on before heavier, oil-based products or creams. The routine order is: Cleanser β Toner/Essence β Niacinamide Serum β Moisturizer β SPF (morning only). It can be used both morning and evening. If using other active serums (vitamin C, retinol, exfoliants), apply niacinamide first or use them in separate AM/PM routines.
No β COSRX The Niacinamide 15 Serum has been independently tested and certified non-comedogenic (comedogenic rating: 0/5). It contains no oils, waxes, heavy silicones or known pore-clogging ingredients. Niacinamide itself is actually anti-comedogenic and helps reduce the sebum buildup inside pores that leads to blackheads and whiteheads. This serum is safe for acne-prone, congested and oily skin without risk of triggering breakouts from the formula itself.
The Period After Opening (PAO) for COSRX The Niacinamide 15 Serum is 12 months. Once opened, use within 12 months for full potency and safety. At a typical usage of 3β4 drops once or twice daily, the 20ml bottle will last approximately 3β5 weeks with daily use, or up to 6β8 weeks if used once daily on the face only. Store in a cool, dry place away from direct sunlight to preserve the stability of niacinamide throughout this period.
Verdict: COSRX The Niacinamide 15 Serum stands out as one of the most potent and cleanest niacinamide serums available at its price point. The clinically-backed 15% niacinamide + 1% Zinc PCA + 2% Acetyl Glucosamine trio delivers genuine, measurable results β including a documented 45% reduction in pore appearance and up to 50% less sebum in 4 weeks. With only 15 ingredients, zero fragrance, fungal-acne-safe status and a pregnancy-safe profile, it checks nearly every box for oily, acne-prone and combination skin types. The main caveats are the small 20ml bottle size and the high concentration which requires a gradual introduction for sensitive skin. For the price, this is exceptional K-beauty value.
