Understanding the structure of the skin, layer by layer, is key to determining what it needs for complete hydration.
The first and main defense barrier is located in the stratum corneum, which is actually the outermost part of the epidermis. This barrier is capable of regulating water loss from our body and the absorption of what we apply to the skin. This "barrier" is made up of mature cells, called corneocytes, which act as "bricks," and the "cement" that binds them is primarily a mixture of lipids. Let's analyze this mortar to better hydrate ourselves.
Although it varies by sex and age, the main component is triglycerides, which is why vegetable oils provide a large quantity of them and are always included in formulas. Waxy molecules also hold a prominent place, so introducing them is always a recommendable option. Among many alternatives, I personally like jojoba oil, which is actually a wax from a chemical perspective, but because it is found in a liquid state, it is called an oil. And it is precisely in this episode that focusing only on functional substances or active ingredients is a mistake, since every single ingredient must be considered, from consistency factors, emulsifiers, humectants, preservatives, viscosity modifiers, essential oils, and perfumes, among many others. Everything must have a reason. Nothing is coincidental, and even less so in natural cosmetics.
With approximately 10% squalene content, it's no wonder it's the star in many products. Despite this, it is a very unstable molecule, and for this reason, we use its less oxidation-prone version, squalane.
At this point, you might be asking yourselves why water, along with other aqueous extracts, is the first ingredient in your usual moisturizer. The answer is simple. In this protective barrier, there are also substances derived from sweat. In fact, many substances found in our blood plasma are found in the aqueous phase of the barrier, known as the hydro-lipid mantle (a combination of water and oil). This mixture contains amino acids (which are the basic constituents of proteins), a carbohydrate called sodium PCA, urea, and various salts of lactic acid.
That said, it makes sense to introduce these molecules to complete and reflect each and every one of them in this protective barrier constantly subjected to climatic and chemical aggressions.