Preservatives in Natural Products: Benzyl Alcohol

The primary focus of Nature’s Pulchritude is to educate.  This post is the fifth in a series of in depth posts that will educate you about the various preservatives in hair and skin products, as well as their potential toxicity.

PURPOSE

Preservatives are added to cosmetics, personal care products, and food to maintain a products integrity and stability by inhibiting or reducing the growth of microorganisms such as bacteria and fungus (FDA).  Most products sold via retail sit for extended periods of time during shipping, in a warehouse, and on store shelfs that allow enough time for a product to spoil or cause microbial growth which render the product unfit for use.  This is particularly true for products that contain water, such as many conditioners and moisturizers, and other active ingredients (antioxidants and emulsifiers) that would otherwise lose their effectiveness and stability over time.

Preservatives are chosen in cosmetics based on a variety of factors which include ability to inhibit growth over a broad spectrum and method of derivation (natural vs. synthetic).  Preservatives tend to be in concentrations less than 2% of the weight of the formula, however, widespread use of potentially harmful preservatives, such as parabens, has been a great cause of concern for some scientists and consumers.  The Food, Drug, and Cosmetic Act does not grant the Food & Drug Administration the authority to regulate the use of preservatives unless it is known to be “poisonous or deleterious” (FDA).

BENZYL ALCOHOL
Chemical Structure of Benzyl Alcohol

Benzyl alcohol is an aromatic (stabilized ring of atoms) alcohol.  Benzyl alcohol is a natural component of many fruits, and is also present in the essential oils of plants such as jasmine and hyacinth.  It is also produced synthetically via the hydrolysis (breakdown of a compound due to reaction with water) of benzyl chloride (C6H5CH2Cl) and sodium hydroxide [lye] (NaOH).  The byproduct of this reaction is benzyl alcohol (C6H5CH2OH) and salt (NaCl).  Benzyl alcohol can also be produced by reacting phenylmagnesium bromide (C6H5MgBr) with formaldehyde (CH2O), which is a known carcinogen.  Benzyl alcohol is used in cosmetics as a bacteriostatic (prevents the growth of bacteria without destroying it) preservative.  Benzyl alcohol is a known skin sensitizer and may also trigger a variety of deleterious effects.  Use of benzyl alcohol is limited to 1% in the EU when used as a preservative, 0.001% and 0.01% when used as a fragrance in leave-on and rinse-off products respectively.  It is limited to 5% in the US.

Hazards
Benzyl alcohol was present in 9% of 204 tested cosmetics products (92 shampoos, 61 conditioners, 34 liquid soaps, and 17 wet tissues), making it the 12th most abundant preservative detected, tied with potassium sorbate (Yazar et al. 2010).  Benzyl alcohol was an ingredient in 24% of 276 moisturizers contained in a database of moisturizers sold at a common drugstore and was the 5th most common allergen (Zirwas and Stechschulte 2008).  Benzyl alcohol is considered an uncommon contact allergen, though it can occur with repeated topical medication or moisturizer use (Zirwas and Stechschulte 2008).  It is most commonly associated with deleterious effects when injected.  Benzyl alcohol was a common preservative in intravascular flush solutions administered to infants, which resulted in “neurologic deterioration and death” in infants with low birth weights (Hiller et al. 1986).  Benzyl alcohol is not likely to cause developmental or reproductive toxicity nor carcinogenicity, though they are suspected mutagens (tests have not confirmed this) (CIR 2011).  It is typically used in concentrations between 0.000006% to 10%, with hair color having the highest concentration.  It has been shown to be a skin irritant or skin sensitizer at 1%concentration in 0.54% and 0.4% of patients, respectively, as well as in 0.3% of patients in a separate study at the same concentration.  It was a skin irritant in 4.9% of patients at 5% concentration (CIR 2011).  It is considered safe up to concentrations of 5% (Nair et al. 2001).

CONCLUSIONS

Benzyl alcohol is a relatively safe preservative when used in cosmetics.  It is not likely to cause dermal toxicity nor is it likely to cause skin irritation or sensitization. Various studies show low rates of irritation and sensitization at 1% and 5% concentration which are within range of allowable usage in cosmetics.  It is not believed to be a carcinogen or a developmental/reproductive toxin in studies.  It is not as common as many other preservatives, though it is more often used in products marketed as natural and organic.  The biggest risk associated with benzyl alcohol is via injection in infants.

 

 

References

Cosmetic Ingredient Review.  2011.  “Amended final safety assesment: benzyl alcohol, and benzoic acid and its salts and benzyl ester.”  CIR.  i-38.

Hiller J., Benda, G., Rahatzad, M., Allen, J., Culver, D., Carlson, C., and J. Reynolds.  1986.  “Benzyl alcohol toxicity:  impact on mortality and intraventricular hemorrhage among very low birth weight infants.”  Pediatrics.  77(4):500-506.

Nair, B., Bergfeld W., Belsito D., Snyder P., Klaassen C., Schroeter A., Shank R., Slaga T., and F. Andersen.  2001.  “Final report on the safety assessment of benzyl alcohol, benzoic acid, and  sodium benzoate.”  International Journal of Toxicology. 20: 23‐50.

Yazar, K., Johnsson, S., Lind, M., Boman, A., and C. Liden.   2010. “Preservatives and fragrance in selected consumer-available cosmetics and detergents.”  Contact Dermatitis.  64: 265-272.

Zirwas, M. and S. Stechschulte.  2008.  “Moisturizer Allergy.”  Journal of Clinical and Aesthetic Dermatology.  1(4): 38-44.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s