[PSA] Lightening ingredients split up by mode of effect. My theory is it's better to use one from each category than double up.

Lightening agents organized by mechanism of action:

Skin turnover accelerators: hydroxy acid, retinoic acid
Premelanin synthesis tyrosinase transcription: Tretinoin
Tyrosinase inhibitors: hydroquinone, azelaic acid, kojic acid, arbutin, soy, peptide, glabridin (from licorice)
Postmelanin synthesis tyrosinase degradation: linoleic acid (in most plant oils), liquiritin (from licorice)
Postmelanin synthesis melanasome transfer inhibition: soy, niacinamide
Antioxidants that chelate copper ions to reduce dopaquinone: vitamin C

This is basically one sentence taken from an article shared by u/rektunicorn -http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4587894/ - but I thought it was a significant enough point to make separately