Zinc oxide reaction with Rosemary extract - is it safe?

I find the colour change that happens in a product that contains zinc oxide and rosemary extract fascinating and I'm aware that it is the oxide reacting with the phenols in the rosemary extract, causing them to oxidise faster (I'm no chemist so please correct me if I'm wrong).

My question and concern is: is the product safe to use when this reaction happens?

I hope someone with much more knowledge than me can enlighten me.


  • @tamicet I believe you're witnessing the catalytic activity of ZnO. I wouldn't actually risk, because it catalyzes many other reactions as well, that may proceed undetected. I'd rather use a coated ZnO instead (or coated TiO2). 
  • @ketchito Thank you for taking the time to reply and explain. You are right, better be safe than sorry!
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