Hydroquinone (Antioxidant or toxin)

One of the most heavily trafficked entries on this site is that on TBHQ. While it's an antioxidant, it's a synthetic one, and some have suggested it might be toxic. Another antioxidant, ferulic acid, found in wheat, works on much the same principle and has found less blame.

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Hydroquinone is, too, an antioxidant, but it exhibits some toxicity and potential carcenogenicity. The lesson that all "polyphenols" are not medicines and all "chemical antioxidants" are not toxins is well taken. The dose, the structure, and (perhaps most importantly) the metabolism make the poison.

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I have some scar lotion that has hydroquinone as the active ingredient. It came with a strict warning not to use it at the same time as any benzoyl peroxide product. Can you explain why that is?

The ultimate unsaturated lipid phenolic antioxidant is nordihydroguaiaretic acid from the creosote bush Larrea tridentata. A few ppm will stabilize lard for decades (WWII use), perhaps centuries. It is now banned from food by the FDA (hepatotoxicity).

Ethoxyquin had its day, especially in animal and pet feed, until hepto- and nephrotoxicity. It appears (human) livers don't like antioxidants other than Vitamins E and C.

Katie, I would guess that the benzoyl peroxide would oxidize the hydroquinone, possibly producing very toxic epoxides.

Co-Q10 is a good example of a quinone/hydroquinone anti-oxidant couple that seems to be well tolerated and has the benefit of being a key player in human metabolism.

Mixing hydroquinone with benzoyl peroxide would be explosively violent, no epoxides formed though, just quinone. Brutal revenge on the acne!