Isopropyl Myristate

In laboratory comedogenicity testing (the rabbit-ear assay), isopropyl myristate and related fatty-acid esters were among the ingredients that promoted follicular plugging, which is why it is often rated highly comedogenic and flagged for acne-prone skin. That said, comedogenicity depends heavily on concentration and the finished formulation, so an ingredient that clogs pores in isolation can behave differently in a real product. If you break out easily, patch-test and see how your own skin responds.

Yes — the Cosmetic Ingredient Review expert panel concluded isopropyl myristate is safe as used in cosmetics when formulated to be non-irritating, and it is permitted in the EU under cosmetics regulations. Undiluted it can be mildly irritating, so its safety depends on the formulation. The common acne concern relates to its pore-clogging potential, not to toxicity.

It is synthetic — an ester made by combining isopropyl alcohol with myristic acid, a fatty acid that occurs naturally in coconut and palm oils. Formulators use it as an emollient and penetration enhancer because it gives a light, silky, non-greasy feel.

It is a skin-conditioning emollient and penetration enhancer that spreads easily and leaves a light, non-greasy slip, so it appears in lotions, cleansers, deodorants and makeup. Because it also helps other ingredients absorb into the skin, it is often used as a texture and feel agent rather than an active.

If you are prone to breakouts it is reasonable to be cautious, since isopropyl myristate has a comedogenic reputation and is one of the esters flagged in pore-clogging studies. Reactions vary from person to person and with how much is in a product, so rather than avoiding it outright, patch-test and consider non-comedogenic alternatives. A dermatologist’s assessment of your own skin is more reliable than any ingredient’s generic comedogenic rating.