Kojic Acid

KOJIC ACID
INCI Name: Kojic Acid

CAS Number: 501-30-4

Product Description
Kojic Acid is a naturally derived skin-lightening agent produced by the fermentation of rice by fungi such as Aspergillus oryzae. It works by inhibiting tyrosinase, the enzyme responsible for melanin production, making it highly effective for fading dark spots, hyperpigmentation, and uneven skin tone.

Used in serums, creams, soaps, and masks, Kojic Acid is a go-to active for brightening and anti-aging formulations. It also offers antioxidant and antimicrobial benefits, helping protect the skin from environmental stressors and breakouts.

Recommended Use Rate
Leave-on products (serums, creams): 0.5–1%

Rinse-off products (cleansers, soaps): 1–2%

Spot treatments & masks: up to 2%

Add during the cool-down phase (below 40°C). Kojic Acid is water-soluble and sensitive to oxidation; store in airtight containers away from light.

Kojic Acid is most stable in slightly acidic to neutral pH ranges, typically between 4.0 and 7.0. Here’s a breakdown of how pH affects its performance and stability:

Kojic Acid – pH Stability Profile
Optimal pH Range:
4.0 to 6.5 — Kojic Acid remains effective and relatively stable.

Below 4.0 — Increased risk of oxidation and discoloration (turns yellow or brown).

Above 7.0 — Decreased efficacy and potential degradation.

Stability Challenges
Oxidation: Kojic Acid is prone to oxidation, especially in low pH or when exposed to light and air.

Discoloration: Formulations may turn brown over time if pH is too low or if metal ions (like iron) are present.

Formulation Tip: Use antioxidants like ascorbic acid, ferulic acid, or sodium metabisulfite to help stabilize it.

Key Benefits
Fades dark spots and melasma

Evens out skin tone and brightens complexion

Antioxidant protection against free radicals

Helps reduce acne scars and discoloration

Suitable for all skin types, especially dull or pigmented skin

Regulatory Note
Kojic Acid is considered safe in cosmetic products at concentrations up to 1% in leave-on formulations. Some regions, like Switzerland and parts of the EU, have restrictions on its use due to potential sensitization concerns.

Formulation Tips
Combine with niacinamide, alpha arbutin, or vitamin C for synergistic brightening

Stabilize with ferulic acid or antioxidants to prevent degradation

Avoid pairing with strong acids (like AHAs) in the same phase to reduce irritation