Combating dark spots: Kojic Acid, a skin whitening agent

Summer time is fabulous with one side effect—a significant increase of sun spots on your face.  I am sure you’ve noticed that, and me too.  Recently, I have been researching into skin whitening agents so I could incorporate those into my summer time weekly facial mask.  Kojic acid emerges as an interesting and effective skin whitening agent.

Kojic acid (chemical name: 5-hydoxy-4-pyran-4-one-2-methyl) is a fungal metabolite derived from various fungal species, especially Aspergillus oryzae, which has the Japanese common name Koji.    The compound is chemically related to hydroquinone and acts as a tyrosinase inhibitor.  Pharmacologically, Kojic acid inhibits skin pigmentation through two biological pathways.  First, kojic acid functions as a chelating agent for copper at the active site of the tyrosinase enzyme and therefore inhibits the catecholase activity of tyrosinase, which is the rate-limiting, essential enzyme in the biosynthesis of the skin pigment, melanin.   Secondly, kojic acid acts as an antioxidant and prevents the conversion of the o-quinone to DL-DOPA and dopamine to its corresponding melanin.  On top of that, Kojic acid is also a free radical scavenger (i.e., antioxidant).

For skin whitening purpose, Kojic acid can be used in a 1-4% composition, either alone or in combination with hydroquinone, tretinoin or a corticosteroid.   A 1996 study suggested that Kojic acid seems to have a better skin whitening effect than conventional skin whitening agent hydroquinone.  (See. Garcia A; Fulton JE Jr., Dermatol. Surg. The combination of glycolic acid and hydroquinone or kojic acid for the treatment of melasma and related conditions. Dermatol Surg. 1996 May;22(5):443-7).  In addition, research seems to suggest that kojic acid works synergistically with hydroquinone and glycolic acid.  The addition of a 2% kojic acid in a gel containing 10% glycolic acid and 2% hydroquinone showed superior results compared to the same gel without kojic acid in one study.  Multiple other studies including Caucasian and Asian patients have shown that combination therapy with 2% kojic acid and hydroquinone improves results.  In a study comparing glycolic acid/kojic acid combination with glycolic acid/hydroquinone, no statistical difference in efficacy was reported between kojic acid and hydroquinone; however, the kojic acid preparation was reported to be more irritating. To decrease the irritation from kojic acid, it is combined with a topical corticosteroid.  In a comparison study, 2% hydroquinone, 10% glycolic acid, and 2% kojic acid decreased hyperpigmentation in patients with melasma better than the same combination without kojic acid.

Kojic acid had been found to cause allergic reactions.  Multiple clinical studies have demonstrated its increased sensitizing potential. It is associated with sensitization, contact dermatitis and erythema.  So, if you want to incorporate this reagent into your skincare formulas, use with caution.

Thanks for reading!
Connie
Connie@cherruby.com

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