What is it?
An oily ester made by joining myristic acid, a saturated fatty acid, with isopropyl alcohol. It is one of the most widely used emollient esters: it softens skin and helps products spread, and it is found in lotions, creams, hair sprays and other hair products, deodorants and eye makeup. It is also used in pharmaceutical preparations, where it helps active ingredients pass into the skin.
Key information
- The CIR Expert Panel found it safe as used in 1982 and again in 2010, and in 2013 included it among alkyl esters that are safe when formulated to be non-irritating.
- In 2013 it was reported in 1,182 cosmetic products, at up to 77 percent in some hair products.
- It is the standard positive control in the rabbit-ear test for pore clogging, where it scored 5 out of 5.
- It helps other ingredients pass into the skin, which is why it is also used in pharmaceutical preparations.
More information
Isopropyl myristate is made by esterifying myristic acid with isopropyl alcohol, then distilling the product. The Cosmetic Ingredient Review (CIR) Expert Panel found it safe as used in 1982 and 2010, and in 2013 included it among 237 alkyl esters it concluded are safe when formulated to be non-irritating; it was then in 1,182 products. Undiluted, it did not irritate 15 volunteers, and repeat patch tests of formulas with 15 to 58 percent on 99 and 320 people found no allergic sensitization. Of 244 people patch-tested for suspected contact dermatitis, 3 reacted. In rabbits, three days of undiluted application was moderately to severely irritating.
The most common concern is pore clogging. Isopropyl myristate is the reference substance in the rabbit-ear assay, and in a 1989 survey it scored 5 of 5 for pore clogging and 3 of 5 for irritation. The author called the model extremely sensitive, and a 2006 study on human skin found that finished products made with comedogenic ingredients are not necessarily comedogenic. Another is penetration: the CIR describes it as a penetration enhancer that stays largely in the skin’s outer layer, and cautions formulators about pairing such esters with ingredients whose safety depends on low absorption. In mice, a 50 percent solution sped up skin tumors caused by the carcinogen benzo[a]pyrene, but isopropyl myristate applied alone did not cause tumors. In the EU’s classification inventory, most company notifications do not classify it as hazardous, but about 16 percent of reports label it a skin irritant.
Reality check: at the levels used, expert reviewers consider isopropyl myristate safe, and allergy to it is uncommon. If you are prone to clogged pores, it is worth watching for in leave-on face products, though how a finished product behaves on your skin is the better guide.
Sources: Cosmetic Ingredient Review: Amended safety assessment of alkyl esters as used in cosmetics (2013); Journal of the Society of Cosmetic Chemists (1989): Comedogenicity and irritancy of commonly used ingredients in skin care products; Journal of the American Academy of Dermatology (2006): A re-evaluation of the comedogenicity concept; PubChem: Isopropyl myristate (CID 8042), GHS classification
