COSRX Alpha-Arbutin 2 Serum: Clinical Results, Irritation Tests and Label Percentages

COSRX The Alpha-Arbutin 2 Discoloration Care Serum, a 50ml serum listed at $25.00 on COSRX's official US store as checked 2026-09-30, pairs 2% alpha-arbutin with tranexamic acid 3%, niacinamide 5% and N-acetylglucosamine 2%, four brightening ingredients that COSRX formulated to target every step of hyperpigmentation, from fresh post-breakout marks to older dark spots. COSRX also publishes the clinical paperwork behind it: a four-week efficacy study, a non-comedogenic assessment on acne-prone skin and a primary irritation test on sensitive skin, all conducted in 2024 by P&K Skin Research Center in Seoul. For readers dealing with acne marks, sun spots or uneven tone, that combination of disclosed percentages and dated test reports is what sets this serum apart from a label that only names its actives.

What the COSRX Alpha-Arbutin 2 label discloses

The front label of COSRX The Alpha-Arbutin 2 Discoloration Care Serum prints its three headline percentages directly: tranexamic acid 3%, niacinamide 5% and NAG 2%. The full ingredient list on COSRX's product page adds the fourth, reading "Alpha-Arbutin(2%)" in seventh position, directly after niacinamide, tranexamic acid and acetyl glucosamine. COSRX calls the set a "multi-target solution" for post-breakout spots: alpha-arbutin, tranexamic acid, niacinamide and N-acetylglucosamine are the main ingredients, and ferulic acid and glutathione are added as synergistic ingredients, six in total aimed at every step of hyperpigmentation.

The same formula carries a soothing layer aimed at skin that is already irritated after breakouts. The ingredient list contains five forms of hyaluronic acid, from sodium hyaluronate to sodium acetylated hyaluronate, plus panthenol, allantoin, madecassoside and tocopherol. On the Korean-market label, the serum is identified as a 미백 기능성 화장품, a brightening functional cosmetic under the framework of Korea's Ministry of Food and Drug Safety, the category for products whose brightening ingredient and concentration have been filed with the ministry. The Korean label names Amorepacific as its manufacturer.

The four-week clinical results

COSRX's efficacy study for The Alpha-Arbutin 2 Discoloration Care Serum followed 20 women aged 20 to 59 over four weeks at P&K Skin Research Center. The study recorded a 20.47% decrease in the amount of melanin on the skin's surface and a 22.31% decrease in the appearance of old, dark spots after four weeks of use. The before-and-after imaging published with the study shows the red melanin area across the cheeks shrinking and facial pigmentation fading toward a more even complexion.

Participants' own assessments pointed the same way. In the same trial, 95% agreed that the serum improved the melanin of their skin, helped reduce visible stubborn dark spots and blemishes, and improved skin tone and brightness. All 20 participants (100%) agreed that their skin felt smoother after use and that the serum's application and absorption were satisfactory.

Non-comedogenic and sensitive-skin testing for COSRX Alpha-Arbutin 2

Post-breakout marks usually sit on skin that is still prone to breakouts, so COSRX ran two separate safety studies on the serum. The non-comedogenic assessment, report PNK-24617-A2RE, was conducted on acne-prone skin from June 17 to July 16, 2024, with 20 participants aged 19 to 59, under principal investigator Beom Joon Kim, M.D., of Chung-Ang University Hospital's dermatology department. The study supports the serum's "non-comedogenic tested" status: a formula that does not clog pores, even on acne-prone skin.

The second study, report PNK-24612-SI12RE, was a primary skin irritation test on sensitive skin with 33 participants aged 20 to 55, conducted June 12 to 14, 2024, and reported on August 7, 2024. It recorded a skin irritation index of 0.00, classified as no irritation, which is the basis for the serum's "suitable for sensitive skin" designation.

How COSRX Alpha-Arbutin 2 compares with Anua and Naturium

Tranexamic acid and niacinamide now appear in several discoloration serums, so the useful comparison is what each label discloses. Anua Niacinamide 10 TXA 4 Serum lists 10% niacinamide and 4% tranexamic acid and sells for $24.00 on Anua's US store. Naturium Tranexamic Topical Acid 5% lists 5% tranexamic acid with kojic acid, niacinamide and licorice root extract, at $20.00 for 1.0 fl oz. Among the three, COSRX The Alpha-Arbutin 2 Discoloration Care Serum is the one that adds 2% alpha-arbutin and 2% NAG to tranexamic acid and niacinamide, and it comes with published efficacy, non-comedogenic and sensitive-skin irritation reports.

Using COSRX Alpha-Arbutin 2 in a routine

COSRX directs users to apply The Alpha-Arbutin 2 Discoloration Care Serum evenly after cleansing and let it absorb, placing it after a toner or booster and before cream. For intensive care, the serum can be layered two to three times as needed. The texture is a fast-absorbing, watery serum designed to leave no residue across skin types and weather. COSRX lists its targets as acne scarring, overall pigmentation, hormonal hyperpigmentation, dull skin and hyperpigmentation caused by tanning or sun damage.

The packaging is built for separation at disposal: a glass bottle and glass dropper tube, a PE dropper wiper, a polypropylene cap and a removable vinyl label. For readers choosing a first serum for post-breakout marks, the combination of disclosed percentages across four brightening ingredients, a Korean brightening functional-cosmetic registration and three dated P&K reports gives The Alpha-Arbutin 2 Discoloration Care Serum an unusually complete paper trail.