What chemicals in skincare products feel oily? I check ingredients before buying facial cleansers and makeup removers, but although different kinds of oils aren’t listed, some still feel oily on my face.

I think you may be describing certain Esters. These are fatty acids made by combining an organic acid with an alcohol (or glycerine) and commonly used in cleansers but possibly wouldn’t alert you to their oiliness from their names alone. Some commonly used are: C12-15 Alkyl benzoate, Caprylic acid, Caprylic/Capric triglyceride, Glyceryl stearate, Isopropyl palmitate, Lauric acid, Myristic acid. These are all produced from coconut or palm oil. They actually tend not to be as oily as the whole fruit oil, but they are emollient.

You may feel a slightly more waxy, rather than oily, feel from Fatty Alcohols. These are made through combining fatty acids with hydrogen. They are often used as emulsifiers (these allow a water ingredient to bind to an oily ingredient), and again, their names do not easily give you their origins: Cetearyl and Cetyl Alcohol are commonly used and come from coconut oil.

I hope this helps, you may be better looking for a serum that is water-based and formulated particularly for skin that requires very little additional oil. I do a vitamin A serum that is used by my customers who really can’t tolerate anything greasy, but still need skin to be hydrated and feel nicely moisturised.