Myristyl myristate is used in a variety of cosmetics and personal care products as an emollient, texture enhancer, and co-emulsifier.
Myristyl myristate is a naturally derived ester, formed by the combination of myristyl alcohol and myristic acid. Myristyl alcohol is a straight-chain saturated fatty alcohol, while myristic acid is a saturated fatty acid with 14 carbon atoms. Both are named after the binomial name for nutmeg (Myristica fragrans), from which it was first isolated in 1841 by Lyon Playfair.
Myristyl myristate naturally occurs in several types of oils and fats. For instance, nutmeg butter is comprised of 75% trimyristin, the triglyceride of myristic acid. In addition to nutmeg, myristic acid is found in palm kernel oil, coconut oil, butterfat, 8 to 14% of bovine milk, and 8.6% of breast milk. Myristyl myristate exists as a white or yellowish waxy solid.
Myristic acid and its salts and esters, including myristyl myristate, may be used in eye makeup, soaps and detergents, hair care products, nail care products, shaving products and other skin care products. It is typically used at concentrations of 1 to 10%.
In cosmetics and personal care products, myristyl myristate functions as an emollient, texture enhancer, and co-emulsifier.
Myristyl myristate is often found in many creams, lotions, and hair care products because it functions as an emollient. It is a soft wax that melts at body temperature, imparting a velvety texture that persists after the rest of the ingredients have been rinsed off. Emollients work to soften and soothe the skin (or hair) while also acting as occlusive agents. Upon application, occlusive agents form a protective film on the surface of skin, which helps to prevent evaporation of the skin’s natural moisture. Over time, this increases skin hydration by causing buildup of water in the stratum corneum (the uppermost layer of skin). These same properties also help to keep the hair soft, hydrated, and manageable.
Myristyl myristate also functions as a texture enhancer when added to formulations of skin care products. Upon application, it provides a soft, slightly waxy after feel. It also gives a product more body and spreadability, as well as a smooth glossy appearance. In certain soap systems, an excess (3.5%) of myristyl myristate produces pearl effects. At very low levels (0.5 to 1%), it improves spreadability of emulsion makeups. It reduces the watery feel of hand and body lotions, and the use of 1 to 1.5% in these products imparts a richness equivalent to having doubled the oil phase. Interestingly, the addition of myristyl myristate to an emulsion can take it from dull gray to bright white.
Myristyl myristate is used as a co-emulsifier for it’s emulsion stabilizing benefits. Emulsions contain both water and oil components. When water and oil are mixed together and vigorously shaken, a dispersion of oil droplets in water – and vice versa – is formed. When shaking stops, however, the two phases start to separate. The combination of fatty alcohol and fatty acids in myristyl myristate thickens emulsions and improves stability making the emulsion much more stable to temperature variations and higher oil and butter levels. Rather than increasing the amount of emulsifier (which would stiffen the product), a co-emulsifier can be used to improve the overall emulsion stability while delivering additional benefits not offered through increased emulsifiers.
The safety of myristyl myristate has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. Both animal and human studies have demonstrated that myristyl myristate does not produce skin irritation or sensitization. Based on these findings, the CIR Expert Panel concluded that myristic acid and its salts and esters (i.e. myristyl myristate) were safe as a cosmetic ingredient in the present practices of use and concentration. According to EWG, myristyl myristate is rated as a 2 to 3 (depending on usage) on a scale of 1 to 10, with 1 being the lowest risk to health and 10 being the highest. EWG reports that some studies have linked it to mild irritation when applied to skin directly.
References: Wikipedia, “Myristic Acid”, Cosmetics Info, “Myristyl Myristate”, Ingredients to Die For, “Myristyl Myristate”, Cosmetic Ingredient Review, “Final Report on the Safety Assessment of Myristyl Myristate and Isopropyl Myristate”, EWG’s Skin Deep Cosmetic Database, “Myristyl Myristate”.