L’acide Kojique: Comment ça marche ?

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Kojic acid-induced IL-6 production in human keratinocytes plays a role in its anti-melanogenic activity in skin.

Choi H, Kim K, Han J, Choi H, Jin SH, Lee EK, Shin DW, Lee TR, Lee AY, Noh M.

J Dermatol Sci. 2012 Mar 14.

Kojic acid is often used to treat various types of hyperpigmentation (ranging from Melasma (Chloasma) (Pregnancy Mask) to Post-inflammatory hyperpigmentation) although more often than not it is widely available without a prescription given even though the cause of the pigmentary disorder is no known.
This wide usage is done with good reason, as the exact mechanism of its anti-melanogenic properties are unknown. A group of Korean medical scientists measured Interleukin 6 (IL-6) and Il-8 in keratinocyte and melanocyte cultures. When adding kojic acid into keratinocytes, Il-6 production was increased (this was not observed in the melanocyte cultures). Also it was observed that the anti-melanogenic effect of Kojic acid was antagonized with anti-Il-6 antibodies.
The authors conclude that Il-6 produced by the keratinocytes when adding kojic acid would explain the inhibition of pigment production.
We would like to add a few comments to this interesting study:

The study is done in vitro and it remains to be seen if this would be observed in vivo. The lack of explanation of its effect in vivo can explain why the response to kojic acid is inconsistent.
Il-6 is a cytokine and as some may know, cytokines have a very non specific action and are chemicals involved in a plethora of functions (ranging from programmed cell death (apoptosis) to inflammation).