Isopropyl myristate is a synthetic oil used in skincare, cosmetics, and some medications to soften skin and help other ingredients absorb more effectively. It’s an ester, meaning it’s formed by combining two simpler compounds: isopropyl alcohol and myristic acid, a fatty acid naturally found in coconut oil and palm kernel oil. The result is a clear, nearly odorless liquid with a molecular formula of C₁₇H₃₄O₂ and a light, silky texture that spreads easily without feeling greasy.
Why It’s in So Many Products
Isopropyl myristate shows up in an unusually wide range of products because it does several jobs at once. It works as an emollient, meaning it smooths and softens skin on contact. It acts as a solvent, helping dissolve other ingredients so they mix evenly into a formula. And it functions as a lubricant, giving creams, lotions, and sprays that slippery, easy-to-spread quality.
You’ll find it in moisturizers, sunscreens, foundations, antiperspirants, bath oils, shampoos, conditioners, hair sprays, nail polish removers, aftershaves, soaps, and cleansers. It’s also used in fragrances, where its value is primarily tactile: it helps perfume oils cling to skin longer and provides a smooth, neutral base that doesn’t interfere with scent.
In topical medications, isopropyl myristate serves as an inactive ingredient that improves how well a drug penetrates the skin. It’s listed in the FDA’s Inactive Ingredient Database for use in pharmaceutical preparations, and it appears in both over-the-counter and prescription topical treatments.
How It Helps Ingredients Penetrate Skin
Your skin’s outermost layer, the stratum corneum, is built like a brick wall. Skin cells are the bricks, and tightly packed layers of waxy lipids are the mortar. This structure is excellent at keeping things out, which is exactly the problem when you want a medication or active ingredient to absorb.
Isopropyl myristate works by embedding itself into that lipid mortar. Because of its branched molecular structure, it doesn’t fit neatly alongside the skin’s natural fats. This mismatch disrupts the orderly arrangement of the lipid layers, loosening them and creating gaps. Research using neutron diffraction (a technique that can visualize molecular arrangements) has shown that isopropyl myristate causes certain skin lipids to separate into a distinct phase, essentially pulling some of the mortar apart. The result is a more permeable barrier that lets active ingredients pass through more readily.
Once absorbed, isopropyl myristate breaks down into its two original components: isopropyl alcohol and myristic acid. Both are substances the body can process without difficulty.
Its Role in Head Lice Treatment
One of the more surprising uses of isopropyl myristate is in treating head lice. A formulation combining it with a silicone-based solvent (cyclomethicone D5) in a 50/50 mixture has been shown to cure 82% of patients with just a 10-minute application, repeated once after seven days.
The mechanism is physical rather than chemical, which is an important distinction. Traditional lice treatments use insecticides that target the nervous system of lice, and over time, lice populations have developed resistance to many of these products. Isopropyl myristate works differently. Head lice depend on a thin waxy coating on their outer shell to prevent water loss. The isopropyl myristate dissolves the specific hydrocarbons that make up this protective wax layer, stripping it away. Without it, lice lose moisture rapidly and die from dehydration. Because the killing mechanism is physical (dissolving a wax layer) rather than biochemical (poisoning the nervous system), lice are not expected to develop resistance to this approach.
What It Feels Like on Skin
Isopropyl myristate has an unusually light sensory profile for an oil. It’s described as smooth and silky, without the heavy, greasy feel of many other emollients. This is one of the main reasons formulators choose it. It lets products feel elegant and absorb quickly rather than sitting on the skin’s surface. The ingredient is nearly odorless. At high concentrations, there’s a barely perceptible oily, faintly fatty quality, but in finished products at typical use levels, you won’t notice any scent from it.
Potential Downsides
The same property that makes isopropyl myristate useful (its ability to penetrate and disrupt skin lipids) can be a drawback for some people. Because it loosens the skin barrier, it may increase the likelihood of irritation from other ingredients in the same product, particularly for people with sensitive or compromised skin.
Isopropyl myristate also has a reputation for being comedogenic, meaning it may contribute to clogged pores. This concern comes primarily from older comedogenicity testing done on rabbit ears, which is an imperfect model for human facial skin. Still, many people with acne-prone skin choose to avoid it, and some dermatologists recommend checking ingredient lists for it if you’re experiencing unexplained breakouts from a new product. If your skin tolerates it well, there’s no particular reason to avoid it. The ingredient has a long safety record in cosmetics and pharmaceuticals.
Physical Properties at a Glance
- Chemical class: fatty acid ester
- Molecular weight: 270.5 g/mol
- Melting point: approximately 3°C (37°F), so it stays liquid at room temperature
- Boiling point: 315°C (599°F)
- Appearance: clear, colorless, oily liquid
- Odor: nearly odorless
Its low melting point and stability at a wide range of temperatures make it easy to incorporate into water-based and oil-based formulations alike, which partly explains its popularity across so many product categories.