Our skin is made up of a number of cell layers and some ingredients can penetrate deep into those layers. If you want your product to go below the surface of skin, you want something that penetrates. There are plenty ingredients that penetrate the skin outer layer, but in the U.S. it is required to be a drug if it actually does that. In order for products to penetrate the skin, an emulsifier (ingredient that holds others together) is typically used to encapsulate the ingredient and deliver the molecules.
Terms like “nanotechnology” and “microspheres” aren’t just fancy-sounding scientific words—these are the key indicators that let you know how a product is being delivered into your skin. Liposomes and niosomes are used to deliver skin penetrating ingredients. (Microencapsulation is the process used: an active ingredient is encased by microscopic capsules or spheres, to preserve the active molecule’s stability, facilitate a controlled release, and enhance penetration through the skin. Certain biologically-active ingredients are fragile and unstable (such as molecules that break down when exposed to light or air). This encapsulation process protects them, and ensures their potency.)
Many ingredients need a special delivery system, but it’s mainly those that are more unstable like retinol, vitamins or certain delicate botanical extracts So what doesn’t need it? Peptides - they are already tiny (peptides are amino acid chains or parts of proteins); essential oils, as they are absorbed via the hair and sebaceous follicle; and hydroxy acids might not require encapsulation. In addition antioxidants are meant to stay on the top layer of the skin, where their action is needed.