Sodium chloride, more commonly known as table salt, functions as a binder, oral care agent, flavoring agent, gentle abrasive, thickener, and preservative in a variety of cosmetics and personal care products.
Sodium chloride is an ionic compound with the chemical formula NaCl. You are most likely familiar with sodium chloride in its edible form as table salt, which is used as a condiment, baking ingredient, and food preservative. Additionally, sodium chloride is the salt that contributes to the salinity of seawater, as well as the extracellular fluid of many multicellular organisms. It is a white crystalline solid.
Sodium chloride is a multifunctional ingredient used in cosmetics and personal care products as a binder, oral care agent, gentle abrasive, thickening agent, and preservative.
A binder is a substance which absorbs water, swells, and helps to hold other ingredients together. Therefore, as a binder, sodium chloride functions to prevent other ingredients used in a cosmetic formulation from coming apart.
You’ll find sodium chloride in products like toothpaste and mouthwash due to its ability to cleanse the teeth and mouth, as well as reduce oral odor. Additionally, sodium chloride is a gentle abrasive, so it can effectively polish the teeth. Sodium chloride also imparts a flavor or a taste to a product.
Since sodium chloride exists as small, crystalline particles, this ingredient can function as a gentle abrasive in products like body and face scrubs. These products will help to exfoliate the top layers of skin, removing makeup, excess oil, dirt, and other impurities that may have accumulated during the day. Exfoliating is crucial in order to maintain clear skin since the build up of extra dead cells on the skin’s surface can clog pores, eventually turning into undesirable acne or other dermal-related conditions. Furthermore, exfoliating becomes even more important as we age since the skin’s natural cycle of shedding dead cells slows down.
Another function of sodium chloride in cosmetics and personal care products is as a thickening agent. Thickeners and gelling agents in the mixtures of organic solvents and water solutions are widely applied throughout the cosmetic industry due to their ability to provide the products with the desired utility features i.e. consistency, viscosity or adhesion. The term viscosity corresponds to the concept of “thickness”, for example, honey has a higher viscosity than water. Sodium chloride can support thickening effects of viscosity enhancers.
Finally, sodium chloride is effective as a preservative due to its ability to reduce the water activity of foods. The water activity of a food is the amount of unbound water available for microbial growth and chemical reactions. The ability of sodium chloride to decrease water activity is thought to be due to the ability of sodium and chloride ions to associate with water molecules. This same mechanism can be utilized to preserve cosmetic products. Just like food, cosmetics products can become contaminated without preservatives, leading to product spoilage and possibly irritation or infections. Microbial contamination of products, especially those used around the eyes and on the skin, can lead to significant problems. Preservatives help prevent such problems, as well as extend the shelf-life of products.
The Food and Drug Administration (FDA) includes sodium chloride on its list of substances considered Generally Recognized as Safe (GRAS). The Cosmetic Ingredient Review (CIR) Expert Panel has deferred evaluation of this ingredient because the safety has been assessed by FDA.
The MSDS for sodium chloride notes that it is, “slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation.”
According to EWG, sodium chloride is rated as a 1 on a scale of 1 to 10, with 1 being the lowest risk to health and 10 being the highest.
References: Wikipedia, “Sodium Chloride”, Truth In Aging, “Sodium Chloride”, Cosmetics Info, “Sodium Chloride”, Institute of Medicine (US) Committee on Strategies to Reduce Sodium Intake “Preservation and Physical Property Roles of Sodium in Foods” 2010, Material Safety Data Sheet, “Sodium Chloride MSDS”, EWG’s Skin Deep Cosmetic Database, “Sodium Chloride”.