We have on our skin a barrier to keep our skin moisturized. It is made up of natural oil that prevents moisture loss from our skin and a natural moisturizing factor (NMF) that keeps our skin moisturized. When we use a strong cleanser, we remove not only the impurities, but also this moisture barrier as well. That is why we use ampoules, serum, lotions and/or creams to put in the moisture lost.
But cosmetics use a number of chemical stabilizers and preservatives to keep the products fresh.
And in most cases, these preservatives could cause various long-term skin problems because of their toxicity. So the amount of usage for these chemicals are regulated by law. If we put layers of these cosmetics, the chemical ingredients in each product can be absorbed and overaccummulated in our skin, which means that more than the legally-allowed amount of chemical ingredients would be absorbed into our skin.
Even if the product is preservative free, it contains stabilizers to ensure that the product is stabilized.
Even if using chemical preservative-free products is better than using ones with chemical preservatives, they still contain chemical stabilizers, which means that layering products with chemical stabilizers would lead to absorption of these stabilizers in an amount that is legally allowed.
It is desirable for cosmetic companies if consumers purchase and layer on different types of cosmetics.
But for those of us who use them, we would not only be layering on chemicals on our skin, but we would be spending too much money to purchase a toner, a lotion and a moisturizer all separately.
Toner, serums, and moisturizers are known to play different functions for our skin; but they differ in viscosity and elasticity and are formulated with similar ingredients. So there is no need to put all these different products on our face. Putting too much can strain your skin. For a healthy looking skin, it is important to use minimum number of products that fully hydrate and moisturize the skin.