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Health Effects of Benzoic Acid, Sodium Benzoate, and Benzene

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

Cinnamon contains benzoic acid.

Cinnamon contains benzoic acid.

Benzoic Acid and Benzoates

Benzoic acid and benzoates are common additives to food, drinks, and other products. They are useful chemicals in manufactured products because they kill or inhibit both bacteria and fungi and can act as preservatives. In general, the chemicals are considered to be safe when they're used in small quantities. They may be harmful in some situations, however.

Benzoic acid was first obtained from the resin of trees belonging to the Styrax genus. The fragrant resin smells like vanilla and is sometimes known as gum benzoin. Today, benzoic acid is often made in the laboratory from other chemicals instead of being extracted from gum benzoin.

Benzoates are derived from benzoic acid and are more commonly used as food preservatives than the acid. Some people develop allergy-like symptoms when they are exposed to sodium benzoate. When the chemical reacts with vitamin C (ascorbic acid) in drinks under certain conditions, benzene may be produced. Benzene is a carcinogen. A carcinogen is a substance that is capable of causing cancer.

Cranberries are a significant source of benzoic acid.

Cranberries are a significant source of benzoic acid.

Benzoic Acid and Sodium Benzoate Facts

Pure benzoic acid is a white to colourless solid that consists of crystalline needles or scales. It's a member of the carboxylic acid family and has the molecular formula C6H5COOH. Benzoic acid is only slightly soluble in water. Sodium benzoate is structurally related to benzoic acid and has the formula C6H5COONa. It exists as a granular powder and is more soluble in water than the acid.

Sodium benzoate is more commonly used as a food preservative than benzoic acid due to its greater solubility in water. Benzoic acid is a more effective germ reducer, however. The benzoate form of the chemical is converted into the acid form in our stomach and absorbed into the body through the lining of the small intestine.

Benzoic acid can be changed into sodium benzoate, and vice versa. If the environment is suitably acidic, benzoic acid predominates. If the environment is not sufficiently acidic and sodium ions are present—as they often are—sodium benzoate predominates.

Benzoic Acid in Food and Other Products

Benzoic acid is found in many plants. Significant amounts are found in some fruits, including cranberries. The chemical is also found in yogurt, certain spices, (such as cinnamon), and honey. Synthetic benzoic acid is added to food and to products such as toothpastes, shampoos, cosmetics, and medicines in order to prevent microbial growth.

Benzoic acid is most effective as a food preservative in an acidic environment. It's thought to generally inhibit the reproduction of bacteria and fungi instead of killing them, but by doing this it can decrease their population. It's believed to interfere with their lives by reducing their ability to use glucose, but it may have other effects as well.

Gum Benzoin and Tincture of Benzoin

Gum Benzoin

Gum benzoin is also known as benzoin resin, gum benjamin, and kemenyan. It's rich in natural benzoic acid and smells pleasant. Two types are available commercially—Siam benzoin and Sumatra benzoin. Siam benzoin is used mainly in the perfume industry, while Sumatra benzoin is used in natural health care.

Siam benzoin is produced by wounding the bark of a tree called Styrax tonkinensis, which is found in Vietnam, Cambodia, Laos, and Thailand. Sumatra benzoin is obtained from the bark of Styrax benzoin, which is native to Sumatra. The injury to the bark of either tree causes a yellow liquid to be released. The liquid hardens into a sticky yellow or red-brown solid.

Tincture of Benzoin

Tincture of benzoin is made by dissolving gum benzoin in alcohol. Compound Benzoin Tincture, Compound Tincture of Benzoin, and Friar's Balsam are three different names that refer to the same product. This product contains gum benzoin and alcohol as well as storax, Tolu balsam, and aloe. Storax is a resin exuded by a type of sweetgum tree, and balsam is another plant resin.

Like gum benzoin, honey contains benzoic acid.

Like gum benzoin, honey contains benzoic acid.

Uses of Compound Benzoin Tincture

Compound Benzoin Tincture (CBT) is a sticky liquid that is applied to skin to improve the adhesion of medical tape and bandages. It's sometimes applied to skin areas that are subject to high friction because it's thought to reduce the chance of blister or ulcer formation.

Some people inhale steam from hot water containing CBT to relieve the congestion of a cold. Care is needed when using this product because it can act as a respiratory irritant as well as a skin and gastrointestinal irritant.

Plums are another natural source of benzoic acid.

Plums are another natural source of benzoic acid.

Potential Dangers of Benzoic Acid

Like most chemicals that have toxic properties, the effects of benzoic acid depend on its concentration. At the low concentrations found in plants and foods, the chemical isn't dangerous for most people. Once it's eaten or produced, benzoic acid is absorbed through the lining of the digestive tract and eventually converted into hippuric acid, which is excreted in the urine.

According to the Material Safety Data Sheet (MSDS) that is created for chemicals, benzoic acid can irritate the eyes, skin, lungs, and digestive tract. Most people aren't exposed to high enough concentrations to experience this irritation, but people who work with the pure chemical or with concentrated mixtures need to be careful. Benzoic acid can enter the body through the skin as well as the digestive and respiratory tracts.

Maraschino cherries are often preserved with sodium benzoate.

Maraschino cherries are often preserved with sodium benzoate.

Potential Dangers of Sodium Benzoate


There are several ways in which sodium benzoate can be harmful to people. For example, it can cause pseudoallergy symptoms in sensitive people. A pseudoallergy resembles an allergy in its presentation, but unlike a true allergy it doesn't involve an immune response.

A skin rash, itching, a runny nose, and congested airways are possible symptoms of a sodium benzoate pseudoallergy. If a person is asthmatic or has a tendency to develop hives, these problems may become worse after exposure to the chemical. It's thought that a response to sodium benzoate is rare in people who don't already have a true allergy. The chemical might play a role in increasing hyperactivity in children, but this is unproven.

Benzene Production

When sodium benzoate reacts with ascorbic acid (vitamin C) in the presence of heat, light, and metallic ions, benzene forms. This reaction may happen in soft drinks that contain the chemicals. This is worrying, since benzene is a carcinogen. In the United States, the FDA (Food and Drug Administration) is aware of the problem. Between 2005 and 2007 the FDA discovered that some soft drinks contained benzene above the allowable level. Since this discovery, many manufacturers have reformulated their products to reduce the amount of benzene.

Benzene Properties and Uses

We are exposed to benzene from a variety of sources, including gasoline at gas stations, car exhausts, emissions from industries that burn coal or oil, emissions from other industrial processes, and cigarette smoke. It's important to avoid adding to the benzene load whenever we can to prevent reaching a critical level that harms our bodies.

A diagram showing the structure of a benzene molecule

A diagram showing the structure of a benzene molecule

Benzene Structure, Dangers, and Concerns

Benzene has many important uses. Before its dangers were understood, it was even used as a reactant in school chemistry experiments. Now it's generally used with caution and only by chemists who know how to handle it.

Benzene was discovered by Michael Faraday in 1825. It contains only carbon and hydrogen atoms and is therefore classified as a hydrocarbon. The benzene molecule is a six sided ring, as shown in the illustration above. The single lines represent single bonds holding atoms together, and the double lines represent double bonds. Although benzene is often represented in this way, chemists have discovered that the bonding between the atoms is not as simple and clear-cut as shown in the illustration.

Benzene exposure may produce acute (immediate) effects if a person is exposed to a large amount of the chemical. These effects may include a headache, dizziness, vomiting, muscle tremors, a rapid or irregular heartbeat, drowsiness, and loss of consciousness. Exposure to a very high concentration of benzene can be deadly.

Exposure to benzene over a longer period of time can affect the bone marrow, decreasing its production of red blood cells and causing anemia. It can also weaken the immune system. In addition, long term exposure to benzene increases the risk of leukemia.

Simplfied Benzoic Acid Structure

In benzoic acid, the ring has a similar structure to that of benzene, but one of the hydrogen branches is replaced by a group of atoms. In sodium benzoate, the H shown in the diagram above is replaced by a sodium ion.

In benzoic acid, the ring has a similar structure to that of benzene, but one of the hydrogen branches is replaced by a group of atoms. In sodium benzoate, the H shown in the diagram above is replaced by a sodium ion.

Although the benzene molecule is dangerous, slightly altered forms of the molecule form part of many larger and generally harmless molecules, including aspirin. Benzoic acid and the various types of benzoates contain the benzene ring but have different atoms attached to one place on the ring. The change in structure often removes the toxicity of benzene.

Significant quantities of benzoic acid have been found in apples. The presence of the chemical may depend on the existence of a fungal infection in the fruit, however.

Significant quantities of benzoic acid have been found in apples. The presence of the chemical may depend on the existence of a fungal infection in the fruit, however.

Safety of the Chemicals in Daily Life

Most people don't need to worry about benzoic acid and benzoates in food, drinks, and other sources, since the chemicals are usually present in small amounts. In addition, most people aren't exposed to high levels of benzene.

Some people do need to be concerned about benzoic acid and sodium benzoate, however, and should reduce their exposure to both substances. It's also advisable for everyone to avoid exposure to benzene as much as possible. We should all be aware of the potential dangers of these three structurally related chemicals.


  • Benzoin information from WebMD
  • Facts about benzoic acid from PubChem, NIH (National Institutes of Health)
  • Benzoic acid and sodium benzoate safety from IPCS (International Programme on Chemical Safety) and WHO (World Health Organization)
  • Questions and answers about benzene in beverages from the FDA (Food and Drug Administration)
  • Benzene in soft drinks from Health Canada

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Questions & Answers

Question: Is benzoic acid a banned substance in Europe?

Answer: Whenever I want to know about safety rules for food chemicals in Europe, I go to the European Food Safety Authority website ( I don’t live on the continent myself, but I haven’t yet seen any reports stating that EFSA has recommended that benzoic acid is banned. In fact, they say that the chemical has low toxicity (as long as the safe amount isn’t exceeded). The website has a search box to help visitors explore the site.

If you do further research, it would be helpful to know the relevant E numbering system that’s used in Europe. Benzoic acid is E 210, sodium benzoate E 211, potassium benzoate E 212, and calcium benzoate E 213.

Question: I have found that foods treated with sodium benzoate cause me to have a really bad and painful intestinal reaction. It is hard to know what is in food these days as one fresh fruit could be treated and the next not. Where can I go to get some help treating this? The doctor I see doesn't even know how to test for such a thing.

Answer: Perhaps you could ask your doctor if a visit to a specialist such as an allergist or a gastroenterologist might be a good idea. An allergist might be able to explore a problem with benzoates. A gastroenterologist would be able to explore whether there is a different cause for your intestinal problem.

© 2012 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on February 08, 2017:

Thanks for the comment, Charlie. You can read my mind! I am going to say that neither the hydrogen peroxide nor the benzoic acid in the solution should be taken internally. To find out whether the amount of benzoic acid in the diluted solution (or the amount of hydrogen peroxide in the dilute solution) is "harmful or negligible" you need to ask your doctor or contact the manufacturer of the solution.

Charlie Berlin on February 07, 2017:

Thank-you for your easy to understand information .

I am even answer readers questions.

This concerns H2O2 solution 6% w/v.

It contains Benzoic acid 0.01% w/v as stabilizer .

I know , you are not a medical doctor .

The manufacturer recommends external use only .

If someone would take up to 10 drops of this solution in water orally , avoiding ascorbic acid at the same time ,..would you say the amount of Benzoic acid entering a body (85 Kg) would be harmful or neglibigle .

I am aware of ,that you can and will not not recommend any internal usage oft his product.

My question concerns just the amount of Benzoic acid entering the body

Thanks again have a great new year


Linda Crampton (author) from British Columbia, Canada on May 27, 2016:

Hi, kaz. I'm sorry about your health problem. It must be so frustrating. I'm not a doctor or a health care provider, so I can't give medical advice to individuals. I would suggest that you visit your doctor, a different doctor or perhaps a dietician to get advice about non-irritating food. You might find toiletries and household products without benzoic acid in health food stores. That's where I go when I want to buy products containing only basic ingredients.

kaz on May 27, 2016:

i was told at the hospital i am allergic to Benzonic Acid. I have a very sore mouth cant wear my dentures , eat mashed potatoes every day ,also have a rash from my head to my feet .Ihave checked my washing liquids and shampoos they all have it, i;m at my wits end can you help me

Linda Crampton (author) from British Columbia, Canada on March 31, 2015:

Thank you, Drew. It's nice to meet you. Your decision to eat fresh and organic food sounds like a great idea!

Drew Lawrence on March 30, 2015:

Thanks for this, very informative. I always stick with fresh and organic!

Linda Crampton (author) from British Columbia, Canada on February 04, 2015:

Thank you very much, Jo. As always, I appreciate your visit and comment, as well as the information that you've shared.

Jo Alexis-Hagues from Lincolnshire, U.K on February 04, 2015:

As a young student nurse many years ago, we used Tincture of Bensoin (Friar's Balsam) as a steam inhaler for patients with breathing difficulties such as bronchitis, I can see why it went out of vogue. An excellent and informative article, meticulously researched. Well done.

Linda Crampton (author) from British Columbia, Canada on June 08, 2014:

Hi, ologsinquito. Thank you very much for the visit and the comment. The potential reaction between sodium benzoate and ascorbic acid is definitely scary!

Linda Crampton (author) from British Columbia, Canada on June 08, 2014:

Thank you very much for the comment, the vote and the share, AnimalWrites. I'm sorry about your sensitivity to food additives. There seem to be quite a lot of people that share your sensitivity!

ologsinquito from USA on June 08, 2014:

This is so informative. It's good to know what can happen when you mix sodium benzoate with ascorbic acid. Yikes.

AnimalWrites from Planet Earth on June 08, 2014:

Thanks for all the great information Alicia, as I'm sensitive to quite a lot of additives and preservatives in food and drinks. Great hub voted up and shared

Linda Crampton (author) from British Columbia, Canada on June 07, 2014:

Hi, midnightbliss. Thanks for the comment. Yes, the number of resources needed to produce goods such as prepared foods can certainly be amazing!

Haydee Anderson from Hermosa Beach on June 07, 2014:

Interesting hub! Honestly, it never ceases to amaze me the countless amount of resources - both organic and synthetic - that are used in the production of various goods.

Linda Crampton (author) from British Columbia, Canada on October 24, 2012:

Hi, Carole. I’m sorry about your son’s health problem. I’m surprised that your doctor didn’t give you a diet sheet when he or she diagnosed your son’s condition. I’m not a doctor myself, and I don’t want to advise you to eliminate a food from your son’s diet if this isn’t necessary!

I found a low benzoate diet that was created by an oral health professor at the University of London. (See the link below.) I suggest that you print the diet and take it to your doctor to see if he or she likes it.

Carole on October 24, 2012:

Hi, my 6 year old son has just been diagnosed with Orofacial Granulomatosis (Oral Crohns) and has been prescribed a Cinnamon & Benzoate Free Diet. Are you able to tell me which foods have the highest natural Benzoate content please?

Linda Crampton (author) from British Columbia, Canada on October 14, 2012:

Thanks for the visit, RTalloni. Yes, fresh food is the best type! It's good to eat as much fresh food as we can compared to other types of food.

RTalloni on October 14, 2012:

Interesting to read up on this common food additive. Thanks for the reminder that fresh is best!

Linda Crampton (author) from British Columbia, Canada on July 02, 2012:

Thank you for the comment, b. Malin. You're so right, everybody's system is different. Sodium benzoate creates no problems for most people but can produce allergy symptoms in others. Reading product labels is very important.

b. Malin on July 02, 2012:

Who knew, so as Always, I say, Thank You Alicia, for your most Informative and Educational Hub read. It's always good to know the side effects of any Chemical, for everyone's system is so different, and allergies can come out of nowhere and become life threatening. I am one that always reads Labels of just about Everything that I buy. Thanks for sharing.

Linda Crampton (author) from British Columbia, Canada on July 01, 2012:

Thanks for the visit and the comment, Nell. Friar's Balsam is certainly interesting! Thank you for sharing your experience with the product.

Nell Rose from England on July 01, 2012:

Hi, I remember very well when I was small having to take Friar's Balsam for bronchial problems, I can even taste it now, it was revolting! lol! but I never realised that it killed bacteria etc, and where it came from. I think the trouble starts as you mentioned when instead of using the natural substance chemists start to add more, this was really interesting and something I had never though off, voted up and thanks for sharing!