Zea Mays Oil

Yes, this ingredient is corn oil. In skincare, it acts as an emollient, skin conditioner, fragrance ingredient, and emusifier.

Like most plant oils, corn oil is basically a bundle of fatty acids: linoleic (34-62%), oleic (19-49%), palmitic (8-12%) and a bit of stearic.

The ranges of the fatty acids differ so much because it varies batch to batch depending on the cultivar and the growing conditions.

In skincare, it mostly does good plant oil stuff: it softens, sits on the surface to slow water evaporation, and makes formulas feel richer.

Now the honest part. Corn oil isn't studied much in dermatology but we do know it's the go-to vehicle in lab research. So there's decades of research where corn oil was the boring control; it never produced an effect of its own but we also don't have much research on it doing something exciting for your skin.

The one thing worth talking about is linoleic. Acne-prone follicles tend to be low in linoleate and a small study found topical linoleic acid shrank microcomedones by around 25% over a month. That was pure linoleic acid and not corn oil so it should be filed under "promising theory" rather than "proven benefit".

Concentration use can be anywhere from trace amounts to about 14% (the high end shows up in cleansers, moisturizers, body creams, and masks). Corn germ oil, which is basically the same ingredient under a different INCI name, has been reported as high as 25% but most of the time you're looking at low single digits.

Corn oil itself isn't a common allergen. Allergies to actual corn are triggered by corn proteins which is mostly refined out of the oil for cosmetic use. How much of the protein removed depends on the manufacturing process, so it's always better to patch test just in case.

Acne

This ingredient does have a comedogenic rating of 0-3, but this doesn't mean a formula with this ingredient will clog pores.

Human testing has proved that any finished product with this ingredient won't automatically make you break out; it really comes down to concentration, formula, and your skin.

Fungal acne

The Malassezia yeast can't make its own fatty acids and breaks down oils around it to feed. Lab research shows the yeast grows when fatty acids in the C11-C24 range are available. Since corn oil is almost entirely C16-C18 fatty acids, this ingredient may not be fungal acne safe.