Cos de Baha Serum 30ml
Cos De BAHA is a Korean skincare brand that labels every product with its active ingredient name and percentage, similar to a clinical actives catalog. The 13+ serums in this 30ml collection cover five categories: brightening (Arbutin 5% + Niacinamide, Vitamin C 15%, Alpha Arbutin + Licorice, Tranexamic Acid variants), fermentation (Galactomyces 94%), hydration (Hyaluronic Acid 1%), and exfoliation (Glycolic Acid 10%, Lactic Acid 12.5%, Azelaic Acid 15%). All are 30ml and ship from Korea.
By Skinsli editorial Updated
Buying guide
Cos De BAHA 30ml Serums: A Guide to All 13 Active-Ingredient Formulas
Cos De BAHA produces a line of Korean actives serums where every product name includes both the ingredient and its concentration, making it straightforward to compare options. The 13+ products in this 30ml collection break into four functional groups: brightening agents, fermentation filtrate, hydration, and chemical exfoliants. This guide explains each ingredient group, what the concentrations mean, and how to choose and layer the serums safely.
Cos De BAHA: A Korean Actives Brand with Transparent Labeling
Cos De BAHA is a Korean skincare brand that follows the transparent-concentration model pioneered by brands like The Ordinary: each product name states the active ingredient and its percentage, which allows buyers to compare potency and make informed stacking decisions. The 30ml format is consistent across the serums, making it straightforward to build a multi-step actives routine with matching bottle sizes. Cos De BAHA products are formulated and manufactured in Korea and are positioned as affordable entry-level actives serums rather than luxury treatments.
Brightening Serums: Arbutin, Vitamin C, Tranexamic Acid, and Niacinamide
The collection includes five brightening serums, each targeting melanin production through different mechanisms. Arbutin 5% + Niacinamide 5% combines two melanin-inhibiting pathways: arbutin slows tyrosinase and niacinamide blocks melanin transfer. Vitamin C 15% inhibits tyrosinase at a clinically relevant concentration. Alpha Arbutin 5% + Licorice Root + Bisabolol is a more complex formula that adds licorice root (glabridin) and bisabolol (soothing) to the arbutin base, making it gentler for sensitive skin. Tranexamic Acid 5% + Niacinamide 5% pairs tranexamic acid (which blocks UV-triggered melanin production) with niacinamide. T15 Tranexamic Acid 15% + Glutathione is the highest-concentration tranexamic acid in the lineup with added glutathione for a secondary antioxidant brightening effect.
Galactomyces Fermented Filtrate 94% Serum: The Fermentation Active
The Galactomyces Fermented Filtrate 94% Serum is one of the highest-concentration ferment serums available in the Korean market. Galactomyces fermentation filtrate is derived from the yeast Galactomyces candidum; the filtrate contains niacinamide, amino acids, vitamins, and enzymes produced during fermentation. At 94%, the serum is mostly the filtrate with minimal additional ingredients. In Korean skincare, galactomyces-based products are associated with brightening, pore-tightening, and overall skin clarity improvement. This serum is used after cleansing and toning, applied generously before heavier serums.
Hyaluronic Acid 1% Solution Serum 30ml: Hydration Foundation
The Cos De BAHA Hyaluronic Acid 1% Solution is the collection's hydration-focused product. At 1% HA concentration in a water-based serum, it is positioned as a standard humectant layer. This serum is compatible with every other product in the 30ml line and is typically applied before more targeted actives. HA 1% is not as concentrated as some premium HA serums on the market, but it is adequate as a skin-priming step before the brightening or exfoliating serums. Apply to damp skin and follow with your chosen actives serum and a moisturizer.
Chemical Exfoliants: Glycolic Acid 10%, Lactic Acid 12.5%, and Azelaic Acid 15%
Three exfoliating serums appear in the lineup. Glycolic Acid AHA 10% is a medium-strength alpha hydroxy acid with the smallest molecular weight of common AHAs, giving it the deepest penetration; it is well-suited to oily or resilient skin with surface texture concerns or congestion. Lactic Acid 12.5% is a larger-molecule AHA that exfoliates more gently than glycolic at equivalent concentration, making it more appropriate for sensitive or dry skin types or first-time AHA users. Azelaic Acid 15% is both an exfoliating and a brightening/anti-acne active; at 15% it is at prescription-adjacent strength and addresses rosacea-related flushing, post-acne marks, and surface texture simultaneously.
How to Layer Cos De BAHA Serums Without Irritation
The most important stacking rule: do not combine two exfoliating acids on the same night. Glycolic 10%, Lactic 12.5%, and Azelaic 15% should be used on separate days or in a rotation (e.g., Lactic on Monday/Thursday, Azelaic on Tuesday/Friday, no AHA on Wednesday/weekend). The brightening serums (Arbutin, Vitamin C, Tranexamic Acid, Niacinamide) are generally safe to combine with each other and with the HA serum, but start with one new active at a time before stacking. Vitamin C 15% should not be used in the same step as niacinamide (they interact to form a flushing compound); use them at different routine times (C in the morning, niacinamide at night) or allow at least 30 minutes between application.
Understanding the Percentages: Which Serums Are Stronger
The percentages on Cos De BAHA serums are directly comparable across the brand. Higher concentration does not always mean better results for your skin; it means stronger activity with more sensitivity risk. The Azelaic Acid 15% and Glycolic Acid 10% are among the most potent products in the range and require a gradual introduction schedule for most skin types. Tranexamic Acid 15% (T15) is stronger than the 5% variant and better suited to skin that has already tolerated the 5% version. The Alpha Arbutin 5% + Licorice + Bisabolol is a gentler formulation than the plain Arbutin 5% + Niacinamide due to the added soothing agents, making it the starting point for brightening on sensitive skin.
Morning vs. Evening Use for Cos De BAHA Serums
Morning routine serums: Galactomyces 94% (antioxidant and brightening without photosensitivity), HA 1% (hydration), Vitamin C 15% (antioxidant + brightening; follow with SPF). Evening routine serums: Glycolic Acid 10%, Lactic Acid 12.5%, and Azelaic Acid 15% (chemical exfoliants that increase photosensitivity - use at night). Brightening agents (Arbutin, Tranexamic Acid, Alpha Arbutin + Licorice) can be used morning or evening with SPF protection in the morning. If using any AHA in the evening, apply broad-spectrum SPF 30+ in the morning to protect the freshly exfoliated skin.
FAQ
Frequently asked questions
FAQ
Frequently asked questions
What is the difference between T15 Tranexamic Acid 15% + Glutathione and Tranexamic Acid 5% + Niacinamide?
The T15 serum is three times stronger in tranexamic acid concentration and adds glutathione as a secondary antioxidant brightener. It is suited for persistent or stubborn hyperpigmentation that the 5% version has not fully addressed. The TA5% + Niacinamide formula is gentler and better for first-time tranexamic acid users or those with sensitive skin. Start with the 5% version for four to six weeks before considering the T15 if you need more intensity.
Which exfoliating serum should I try first: Glycolic Acid 10% or Lactic Acid 12.5%?
If you are new to chemical exfoliants, start with Lactic Acid 12.5%. Despite the higher number, lactic acid is gentler than glycolic at equivalent concentrations because its larger molecular size means slower, shallower penetration. Glycolic Acid 10% is the stronger of the two and is better suited to oily or resilient skin that has already used AHAs before. Both should be introduced gradually: once per week first, then build to two to three times per week over four to six weeks.
Can the Cos De BAHA Azelaic Acid 15% help with rosacea-related redness?
Azelaic acid is one of the few actives with documented efficacy for rosacea. It reduces inflammatory papules, normalizes keratin production, and has antimicrobial properties relevant to rosacea-associated bacteria. At 15% it is near the prescription-strength (20% is the clinical standard), so it is likely to show measurable improvement with consistent use. Introduce it slowly (once per week) and increase frequency as tolerated. If you have active rosacea flares, consult a dermatologist before starting any new active.
What does the Cos De BAHA Galactomyces 94% Serum do for skin?
Galactomyces fermentation filtrate contains niacinamide, amino acids, vitamins, and enzymes that contribute to pore-tightening, brightening, and overall skin clarity. At 94% concentration, this serum is nearly pure filtrate. Regular morning use is associated with more even skin tone and reduced pore visibility over four to eight weeks. It is one of the gentler actives in the range and is compatible with sensitive skin.
Can I use the Vitamin C 15% Serum and the Arbutin 5% + Niacinamide 5% Serum in the same routine?
Apply them at different times. Vitamin C and niacinamide together in high concentrations can form nicotinic acid, which causes temporary flushing and redness. Use Vitamin C 15% in the morning routine and Arbutin + Niacinamide in the evening routine. If you prefer to use both in the same routine, wait at least 30 minutes between the two applications. The risk is temporary and not harmful long-term, but the redness is uncomfortable.
Is the Alpha Arbutin 5% + Licorice Root Serum gentler than the Arbutin 5% + Niacinamide Serum?
Yes. The Alpha Arbutin + Licorice + Bisabolol formula adds soothing agents (bisabolol is a calming active from chamomile; licorice root has anti-inflammatory properties) that reduce the risk of irritation. For sensitive or easily reddened skin, the Alpha Arbutin + Licorice version is the better starting point. The Arbutin + Niacinamide serum is more straightforward in its active combination and well-tolerated by most skin types, but lacks the additional soothing layer.
How many Cos De BAHA serums can I use in the same routine?
Most people use one to three serums per routine step. A common combination: HA 1% (hydration base), one brightening serum (Galactomyces, or one of the arbutin/tranexamic options), and one exfoliant (evening only). Applying more than two or three leave-on actives per session increases irritation risk without proportional benefit. Add one new serum at a time, spaced two to three weeks apart, to identify any reactions before stacking further.
Is Cos De BAHA a Korean skincare brand?
Yes. Cos De BAHA is a Korean skincare brand that produces its serums in South Korea. It follows a transparent-concentration formula labeling approach and sells its products through Korean beauty distribution channels including skinsli, which ships them directly to US customers.