You find thousands of moisturizing products on the market. What do they all have in common?
Constituents in moisturizers can be divided into 3 categories of ingredients that work together to maintain your skin moisture level: humectants, emollients, and occlusives.
To understand the purpose of these categories, it is important to start with understanding the structure and the function of our most outer skin layer.
Our skin acts as a barrier that protects us against outside environment and the moisture loss. The most outer layer of our skin called stratum corneum and it is composed of dead cells called corneocytes, which are filled with the protein keratin. These form protein-based ‘bricks’. In between these cells is a mixture of compounds, primarily lipids, that act as the ‘mortar’, holding the ‘bricks’ together. Lipids mainly consist of a mixture of ceramides, cholesterol, and fatty acids, play an important role in allowing the skin to retain water, as they form a semi-permeable barrier to water. Normally our skin loses some of its water content through evaporation. To address the moisture loss, the water is the main ingredient in moisturizers. When moisturizer is applied, some of this water will soak into the skin, but some will evaporate. To prevent evaporation, moisturizer includes one or several humectant ingredients. Humectants bind to the water and hold it onto the skin. Examples of humectants include glycerin, amino acids, panthenol (vitamin B5) and hyaluronic acid. A moisturizer may also include occlusive ingredients, mostly oil soluble, that create a water-resistant, physical barrier over your skin to seal in moisture and prevent the evaporation of water. Vegetable oils and butters high in oleic fatty acid content, such as olive oil and cocoa butter are examples of occlusive ingredients. Emollients are lubricating, filling in spaces between skin cells and supporting the lipids, the ‘mortal’ component of the stratum corneum, resulting in softened and smooth skin. Examples of such ingredients are vegetable oils, such as grapeseed and rosehip oils. Emollients, humectants and occlusives work together to maintain the skin's moisture level.
Additionally, in moisturizer you’ll find structural ingredients to create a stable consistency, antioxidants to help shield skin’s surface from oxidation, preservatives to prevent growth of bacteria, fungus and mold. Some moisturizers bring you additional benefits in a form of active ingredients to aid skin rejuvenation.
There are numerous ingredients in each category and the combinations of these ingredients create a variety of products you find in stores and online.
Check the ingredient list of your moisturizer to identify occlusive, humectant and emollient ingredient.