Dry skin, also called xerosis, is a common condition experienced by most people at some point in their lives. It tends to be quotidian during cold, dry weather, and also tends to become more common with age as NMF (Natural Moisturizing Factor) levels, and sebaceous gland activity, decline. People with inflammatory skin conditions like dermatitis and psoriasis, and those with hereditary disorders such as ichthyosis, are also predisposed to the development of dry skin.
Key Components of Moisturizers
Moisturizers are the main player in the fight against dry skin. The ingredients that make them effective against dry skin conditions can be classified into three main categories, each with its own advantages and disadvantages. The best moisturizers tend to effectively combine all three in a single formula. The categories are:
Emollients. These are oily substances that fill in the gaps between dead skin cells, smoothing out the skin’s surface and aiding and abetting its barrier function. While emollients do have some occlusive effects, their primary function is to soften the skin. Examples include butters and oils, esters, fatty acids, and ceramides. Emollient moisturizers are beneficial for everyone. Not all emollient ingredients are suitable for everyone however, and which emollients you should look for, or avoid, in moisturizers depends largely on your skin. Individuals with acne-prone skin, for example, should avoid emollients like coconut oil and cocoa butter as these tend to clog pores and cause breakouts.
Occlusives. Occlusives can be thought of as a second skin. They create a physical barrier atop the skin’s surface to help reduce the rate of trans-epidermal water loss and prevent the skin from getting dehydrated. Examples include petrolatum, lanolin, certain silicones and waxes. Occlusives tend to be best for individuals with drier skin types and those prone to dry skin conditions like eczema and psoriasis.
Humectants. These are hygroscopic substances, i.e., substances that tend to absorb moisture from the air to hydrate the skin. For the chemistry nerds out there, at a molecular level humectants are able to absorb and hold onto water due to the presence of hydrophilic hydroxyl and amine groups that make the molecule polar, thus allowing it to create hydrogen bonds with water molecules. Humectants are able to draw water vapour from the air to help hydrate the skin if the humidity level is above 50%. At lower levels of humidity, they can sometimes pull up too much water from deeper layers of the skin from where, due to a lack of atmospheric humidity, it subsequently evaporates at an accelerated rate, ultimately leading to skin dehydration. Examples of humectants include the very hyped hyaluronic acid, urea (my personal favourite, followed by glycerin), amino acids, sugars, honey, and even alpha-hydroxy acids, among several others. Hydration is essential for the normal functioning of skin, including the process of desquamation, i.e. the natural shedding of dead cells from the skin’s surface. This makes humectants beneficial for all skin types. They are however, especially beneficial for individuals with drier, more dehydrated skin. Lastly, humectants also provide temporary anti-ageing effects as extra hydration plumps the skin up, making fine lines and wrinkles less noticeable. It is important to note however, that this impact is transient and humectants are not a substitute for anti-ageing ingredients like retinol.