Kojic Acid: The Thyroid Peroxidase Inhibition Finding
Kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone) is a fungal metabolite derived from *Aspergillus* species that inhibits tyrosinase by chelating the enzyme's catalytic copper ion.
In its toxicology audit (SCCS/1641/22), the EU committee evaluated systemic absorption data. The review concluded that while kojic acid is safe at low concentrations, concentrations above 1% pose potential endocrine-disrupting risks by inhibiting thyroid peroxidase, altering circulating thyroid hormone levels (T3 and T4) and prompting thyroid follicular cell hyperplasia.
Alpha Arbutin: The Hydroquinone Hydrolysis Risk
Alpha Arbutin is a glycosylated hydroquinone derivative. The European Commission restricted Alpha Arbutin to 2% in facial creams and 0.5% in body lotions due to concerns over formulation stability.
Under prolonged storage, elevated bathroom heat, or low pH (below 4.5), the glucoside bond can undergo chemical hydrolysis, liberating free hydroquinone. Hydroquinone is strictly banned in over-the-counter cosmetics in the European Union due to cellular melanocyte toxicity and exogenous ochronosis risks.
Safer, Non-Restricted Depigmenting Alternatives
For consumers seeking to treat melasma and post-inflammatory hyperpigmentation without regulatory toxicity concerns, two actives remain completely unrestricted and non-endocrine disrupting:
1. Azelaic Acid (10–20%): Selectively suppresses hyperactive melanocyte tyrosinase with zero systemic endocrine interference.
2. Tranexamic Acid (2–5%): Blocks the vascular plasminogen/plasmin pathway that stimulates melanocytes without any hydroquinone cleavage risks.
Formulation Takeaway: Check your dark spot serums. Ensure Kojic Acid is formulated at 1% or below. For chronic long-term hyperpigmentation management, switch to Azelaic Acid and Tranexamic Acid.