Hydration vs. Moisturization: They’re Not the Same Thing!
Hydration vs. moisturization is an ongoing topic of conversation in the skincare world. Social media influencers like Dr. Anjali Mahto, Hyram, and Susan Yara have all shed some light on the subject (showcasing varying degrees of technical prowess), while many beauty/lifestyle media platforms have done the same. Given it’s winter time and this theme is top of mind for many of us, we want to get our word out on the matter, too.
Here’s the thing – many people, including brands, use the terms hydrate and moisturize interchangeably when, in fact, they do not mean the same thing. Semantics matter, and if we all paid more attention to it, then the beauty world could be less confusing. Wouldn’t y'all agree?
The root of all the confusion primarily has to do with the following: 1) we formally define both moisturize and hydrate almost the same way in the dictionary, 2) the term ‘moisturizer’ is a misnomer and should be called something like a ‘sealer’ and 3) old school chemistry has traditionally classified emollients, humectants, and occlusives as different types of ‘moisturizers,’ clumping them together under one umbrella.
So what’s the truth behind hydration and moisturization in terms of our skin care products and routines? It’s pretty straightforward and we’re keeping it short and sweet. Let’s dig in.
First things first, skin hydration relates to the concentration of water in the stratum corneum (the outermost layer of our skin), while moisturization relates to skin suppleness and smoothness, based on the lipidic material (the ceramides/fatty acids/cholesterol found in between cells, or the ‘mortar’ in the bricks and mortar model) of our skin barrier.
Hydration and moisturization can be essential in achieving healthy skin, regardless of your skin type or your environment. There are three categories of skincare ingredients with different mechanisms of action that deliver hydration and moisturization: humectants, occlusives, and emollients.
Hydration = Humectants
Humectants (e.g., hyaluronic acid, glycerin, urea, sorbitol, amino acids) are typically water-soluble hygroscopic organic compounds that draw water from the body or the environment to help maintain a healthy hydration level in the skin. These are the ingredients that infuse moisture and are particularly useful for those of us with dehydrated skin. In terms of your skincare regimen, product formats like toners, essences, and serums (which are applied early on in your routine) may feature a base of water/aqua, aloe vera juice, or a green tea infusion, for example, and humectants like hyaluronic acid or glycerin. These make excellent hydrating products.
A point to remember: our skin naturally has its reservoir of water, in the form of natural moisturizing factors (NMFs), which exist inside corneocytes (our dead skin cells) in the stratum corneum. NMFs include humectants like lactic acid, amino acids, HA, urea, and sodium pyrrolidone carboxylic acid. Humectants in our skincare products support the skin’s natural water-holding system.
Moisturization = Occlusives & Emollients
Occlusives, such as hydrocarbon oils/waxes (e.g., petrolatum, mineral oil, dimethicone), esters (e.g., caprylic/capric triglyceride, isopropyl myristate), wax esters (e.g., beeswax, lanolin), or plant oils, form an inert layer on the skin and help prevent trans-epidermal-water loss. The more your skin is able to retain water, the more optimally it will function. So occlusives do the heavy lifting by helping to seal in the hydration, not deliver it.
Emollients are equally important in the moisturization game. They are usually oil-soluble softening agents that, at times, overlap with occlusives in terms of functionality (e.g., dimethicone, plant oils, butters). Emollients condition the skin and improve its overall texture and appearance. Oftentimes they are biomimetic – in other words – they resemble the lipids or ceramides/cholesterol/fatty acids of our skin barrier and work well to address dryness (lack of oil) and to protect the skin. We like Cassandra Bankson’s reference to a silk satin ribbon when talking about emollients; these saturated or unsaturated hydrocarbons make your skin feel silky, smooth, and soft. Common examples of emollients include Ingredients like squalane, coconut alkanes, or various butters and plant oils.
An important thing to remember is that any well-formulated moisturizer (e.g. lotion or cream) typically features a combination of hydrating and moisturizing ingredients (humectants, emollients, and occlusives). They all work together to support the water and lipid content of the stratum corneum.
So, there you have it. A simple and useful guide to hydration vs. moisturization. As Hyram says, the skincare education grind never stops, and we’re here to support you on that journey. Until next time.