Inositol is an ingredient used in cosmetics and personal care products as a humectant moisturizer, a multi-action tanning compound, and an anti-static agent.
Inositol, also known as myo-inositol, is a carbocyclic sugar that the human body naturally produces from glucose by the kidneys. The highest concentration of inositol in the human body is in the brain where it plays an important role making neurotransmitters and some steroid hormones bind to their receptors. Inositol is sometimes mistakenly thought of as a B vitamin, however, it is not a vitamin because it can be synthesized by the body.
For use in cosmetic formulations, inositol is prepared from an aqueous (0.2 percent sulfur dioxide) extract of corn kernels by precipitation and hydrolysis of crude phytate. Inositol can also be extracted from the fruits of Ceratonia siliqua, the carob tree.
In cosmetics and personal care products, inositol functions as a humectant moisturizer, a multi-action tanning compound, and anti-static agent.
Inositol can be classified as a humectant moisturizer. A humectant is a hygroscopic substance that has a molecular structure with several hydrophilic (water loving) groups. This structure allows humectants to attract and retain the moisture in the air nearby via absorption, drawing the water vapor into or beneath the surface. Humectants improve moisture retention and may also help other topical skin care ingredients to perform better. For this reason, inositol is often found in creams, lotions, facial moisturizers, and anti-aging skin care products.
Additionally, inositol is a major component of lecithin, another ingredient used in skin care products due to its functions as an emollient, emulsifier, and penetration enhancer. Lecithin is a very beneficial ingredient because it creates a barrier on the skin that effectively seals moisture in while keeping air and other environmental elements out. This property makes lecithin an excellent ingredient to add to restorative creams, or for products designed for mature, dry, or overworked skin.
Another function of inositol in skin care products is as a multi-action tanning compound. Inositol has the ability to intensify and maintain a suntan longer by activating the main melanogenesis pathway. It can be used in “before-tanning” formulations such as sunscreens, tan accelerators, and day facial creams, as well as “after-tanning” formulations such as tan-prolonging products and after-sun creams and lotions.
The final function of inositol in cosmetics and personal care products is as an anti-static agent.
An antistatic agent is a compound used for treatment of materials or their surfaces in order to reduce or eliminate buildup of static electricity. Humectants like inositol work well as anti-static agents because they absorb moisture from the air and make the surface or the material itself slightly conductive. Anti-static agents are primarily used in cosmetic packaging.
The United States Food and Drug Administration (FDA) lists inositol as a direct food substance affirmed Generally Recognized As Safe (GRAS). The safety of inositol has not been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. However, the Panel did evaluate the safety of lecithin as used in cosmetics, and inositol is a major component of lecithin. The Panel evaluated the scientific data and concluded that lecithin is safe as used in rinse-off products. However, the Panel limited the use of lecithin in leave-on products to concentrations less than or equal to 15 percent. According to EWG’s Skin Deep Cosmetic Database, inositol is considered to be safe as used in cosmetics and personal care products. It 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 “Inositol”, Making Cosmetics “Inositol”, Revolvy.com “Anti-Static Agent”, Cosmetic Ingredient Review “Safety Assessment of Lecithin and Other Phosphoglycerides as Used in Cosmetics” 2014, FDA Code of Federal Regulations “Inositol”