Do Sodium Benzoate and Vitamin C react to form carcinogenic benzene?

Sodium Benzoate and Vitamin CAn intriguing query from an individual who calls themselves simply B.


I’ve been looking around online on topics related to Sodium Benzoate and Vitamin C as I have read that when these two ingredients are mixed it can form Benzene which is a known carcinogen. I’ve been looking for a good Vitamin C serum for a while now but most of the ones I encounter contain Sodium Benzoate.
What are your thoughts on this? Are the amounts of Vitamin C and Sodium Benzoate so small it would not react to create Benzene and if it was formed would it be harmful?
Thank you!

This is an interesting one.  The story about benzoic acid being converted into benzene was one that started in the soft drinks industry.  Benzoic acid has been used in soft drinks which also contain vitamin C, and benzene has been found in them. The reaction where benzoic acid is broken down into benzene is one that you find in the organic chemistry textbooks.  What the text books also reveal is the optimum conditions for the reaction to occur. These are a long way from what you find in soft drinks, and the levels of benzene found were extremely low. The trouble with molecules is they are very small and there are lots of them.  So even though the chances of forming benzene are low with billions of molecules around some of them manage to react even though the conditions for the reaction are not very favourable.  Even that doesn’t seem to be the whole story because when the UK’s FSA investigated they found that not all the drinks that theoretically could have contained benzene actually contained it.  So either there is another factor that is needed to promote the reaction that we haven’t identified yet, or the benzene was actually coming from some other source altogether.

In most cosmetic products the conditions would be even less favourable. And you don’t eat them.  So on the whole I don’t think there is much risk of benzene actually being created in cosmetic products, or of it doing any harm if it were.  It would be much less exposure than you probably get to benzene when you fill your car with petrol. So I think this is a non issue really, but I enjoyed getting my old chemistry book out.

8 thoughts on “Do Sodium Benzoate and Vitamin C react to form carcinogenic benzene?”

  1. Thanks for your comment Pedro, but I was addressing the question of benzene being formed in situ in cosmetics. I am not disputing that it has been found in soft drinks. I don’t even dispute that there used to be some in cosmetic products. I have written a blog post on it

    But far and away the biggest source of benzene in our lives is in petrol.

  2. Thanks Colin for answering my question – much appreciated! It’s so hard to know nowadays what is real or just scaremongering on the internet. I guess you can never be too safe but like you said there are plenty other things in life that can cause cancer. Everything in moderation I guess.

    I shall use that Vitamin C Serum that I bought now.

  3. While you may not eat cosmetics products as Colin says, our skin absorbs whatever we put onto it, at least to a degree.

    So really the comment about cosmetics containing sodium benzoate and Vitamin C not being dangerous because we don’t consume cosmetics isn’t as clear sut as it might at first appear.

    If it enters our tissues, either through absorbtion or ingestion (even if the two are ingested or absorbed separately at close, but different times the potential danger remains the same.

  4. Pía Carolina

    I’m using this body scrub which contains sodium benzoate and ascorbic acid (Honey & Shea body scrub by Burt’s Bees), and suddenly I found out what happens when they are together (benzene!) and I freaked out. I started to read information online and got to this post, I read your thoughts about it, and felt better… but then I read Spikey’s reply: “while you may not eat cosmetics products as Colin says, our skin absorbs whatever we put onto it, at least to a degree (…). If it enters, either through absorbtion or ingestion the potential danger remains the same”, and I freaked out again. I will certainly not repurchase this scrub again, but it was so expensive that I think I will use it up until it’s finished. Will it be safe, you think??

  5. Thanks for your comment Pia. I don’t think Spikey, whoever he or she is, knows what they are talking about. The skin is an exceptionally good barrier to most things. Here is a good way to illustrate this. Someone has calculated how to get the same effect as taking an aspirin tablet by using a medical patch. You would need to cover two thirds of your body.

    It so happens that benzene is one of the few chemicals that can penetrate the skin without being blocked. But it also vapourises into the atmosphere at the same time, so you will still get relatively little through the skin. As I say in the post, your exposure from benzene in petrol is going to dwarf anything from your scrub. That is if there actually is any in there in the first place – as I pointed out even in the soft drinks it seems that something else is necessary for the benzene to form.

    But aside from all that, scrubs don’t need to be expensive so why not look for a better one anyway.

  6. Pía Carolina

    Thank you so much for answering this fast. I always read the ingredients list on the products I buy, but this time I just trusted cause it was Burt’s Bees and the packaging said “100% all natural”. After I finish this “hazardous” scrub (I won’t throw it away just because it cost me a lot, where I live these things are twice more expensive) I have I’m going to create my own one, using only things I know well: coconut oil+sugar+honey, or coconut oil+ground coffee, things like that. Thanks again!

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