Benzoic acid is an ingredient that is common in many types of skin care products, but often suffers from mistaken identity. The name of the substance is similar to that of benzoyl peroxide, a medicinal ingredient often used in the treatment of acne. Despite the similarity of their names, benzoic acid and benzoyl peroxide are not the same ingredient and do not offer the same benefits for the skin. Benzoic acid is, however, a building block of benzoyl peroxide and mixes with oxygen to form the substance. Benzoic acid is also sometimes confused with benzoin resin, from which benzoic acid is derived, and with the organic compound benzoin, which is used to protect building and industrial materials from sun damage.
In its natural state, benzoic acid is colorless and looks as if it were comprised of thin, shiny shavings due to the natural shape of its crystalline structure. The ingredient is classified as a weak acid and is comprised of carbon, oxygen and hydrogen. Benzoic can also be referred to as carboxybenzene and E210.
Benzoic acid is found in a variety of plants, including apricots, cranberries, mushrooms and jasmine. Some invertebrate species also contain benzoic acid. Although the ingredient can be derived from its natural sources, it typically is made through synthetic means, as manufacturing the ingredient is less expensive and can result in greater yields.
Approximately 139,000 tons of benzoic acid are produced synthetically each year for use in a variety of industries. To manufacture benzoic acid, a liquid called toluene is mixed with oxygen, and then a compound that contains cobalt or manganese is added to the solution to hasten the reaction that occurs. The majority of the synthetically produced benzoic acid is converted to esters and salts, which can be used as ingredients in numerous products. Only a small amount of benzoic acid is added to products in its natural form.
The history of our knowledge of benzoic acid dates back to the 16th century. It was then that Nostradamus described how benzoin resin could be broken down into its raw components through the use of distillation. Nostradamus could not fully isolate the acid, and he did not give it a name. It was not until 1832 that the exact composition of benzoic acid was discovered by the scientists Justus von Liebig and Friedrich Wöhler.
One of the earliest uses of benzoic acid was in the treatment of infections, particularly those caused by fungus, such as ringworn and athlete's foot. The acid is still used as an active ingredient in a small number of topical anti-fungal medicinal solutions that are available as over-the-counter creams, ointments and lotions.
The most common modern use of benzoic acid in personal care products is as a preservative. The anti-fungal nature of the ingredient helps prevent mold from growing within the packaging of products. It is also a mild antibacterial, which means it protects products from bacteria as well. Typically, benzoic acid is used in toothpastes, moisturizers and other skin care formulas that are acidic in nature.
Because it is milder than other types of chemical preservatives, benzoic acid is often found in products designed for sensitive skin. Benzoic acid that is derived from plants or invertebrates may also be used as an alternative to chemical preservatives in natural skin care lines.
The U.S. Food and Drug Administration lists benzoic acid in its "Generally Regarded as Safe" category. This means that benzoic acid is not known to be toxic in its raw form. The EPA has listed benzoic acid as having no carcinogenic or cancer-causing ability since 1986. Typically, when used in strengths of 5 percent or less, benzoic acid does not cause side effects. When people do experience sensitivity to benzoic acid, their symptoms are generally mild and include skin redness and minor itching.
Some studies have found that benzoic acid may be unsafe when combined with vitamin C. Evidence gathered from these clinical trials has suggested that together the substances form benzene, a chemical that has been linked to some forms of cancer. If benzene forms in products that contain both vitamin C and benzoic acid, the quantity of the chemical is very minimal. It is not known whether exposure to such small amounts could have any long-term health effects.