If you read beauty blogs, browse natural hair forums or scan the blurb on product labels, you've probably heard this line being drawn between moisture and hydration... and been a little confused by it.
Can there really be a difference between moisture and hydration? If so, what is it?
The difference between moisture and hydration
Let's cut to the chase: technically, there is no difference between moisture and hydration. So why do some naturalistas, influencers and marketers alike swear there is?
Ask any cosmetic scientist - the formulators who design everything from shampoo ingredients to skin serums - about the difference between moisture and hydration and you'll get some variation of this answer: there is no difference.
Scientific papers from the field underline this: moisture and hydration are used interchangeably by the people who actually make and research the stuff we use on our hair and skin. From hydration studies which look at the "distribution of water in the hair", to review articles which use the terms "water content" and "moisture content" as synonyms, there is no distinction. Moisture = water, and hydration = water, therefore moisture = hydration.
Both moisture and hydration are synonyms for water. Image by The Creative Exchange.
Ask a beauty blogger or aesthetician, though and you'll get any range of answers setting out the finer points of the moisture or hydration distinction, based largely on products which include either of these synonyms in their names or product descriptions.
But what most people don't realise, is that product names are usually created by marketers,who typically have no cosmetic science background. A brand's marketing department makes their decisions on what they want to call a product based on the image they'd like to conjure for consumers, rather than any material difference in product performance.
In science, the closest you'll get to the moisture-hydration distinction drawn in the consumer space, are two concepts often used by hair scientists: "moisture restoration" and "water retention". In this rough analogy, a product that provides "hydration" would be one that offers moisture restoration, while a "moisturising" product would help with moisture retention.
What is moisture?
Moisture is, of course, water. That's it. No other ingredient is moisture apart from good ol' H2O. That's why natural veterans get so annoyed every time a newbie natural claims to be 'moisturising' their hair with oils when in reality they're just coating over dry hair and making it even drier.
But that's another story. So while moisture = water, a moisturizer is something different. Moisturising products are the ones that either enhance your skin or hair's water content (also known as its "hydration state") or protect it from moisture loss. And to do this job, moisturizing ingredients don't need to contain water. They can include:
Humectants: Ingredients like glycerine, hyaluronic acid, sorbitol, lactic acid and propylene glycol that attract moisture.
Occlusives: Ingredients which prevent moisture loss, such as petrolatum, beeswax, vegetable oils, silicones, fatty alcohols and fatty acids.
Emollients: Ingredients that smooth and soften the skin or hair, replacing lost lipids and providing lubrication and protection. Many emollients do double duty as occlusives: petrolatum, beeswax, vegetable oils, silicones, fatty alcohols and fatty acids are all emollients.
(Skin) rejuvenators: Ingredients that improve barrier function on the skin and strengthen the hair's protective layers like proteins and ceramides.
Glycerine is the most common humectant in skin and hair products. Image by Daria Nepriakhina.
Note that when it comes to occlusives, for these to do their job, they either need to be included in a product base that actually contains water, or applied on wet hair or skin (damp with a water-containing product counts as "wet"). That's why using oil on dry hair doesn't count as moisturising unless your hair already has ideal moisture levels that you're trying to maintain.
Most skin and hair products include a mix of all of these different types of "moisturising" ingredients, whether they say "hydrating" or "moisturising" on the label.
What is hydration?
Hydration = moisture, water.
Perhaps because of its name, "hydration" invokes water a lot more than "moisture". So while cosmetic scientists don't see a difference, the marketers who name the products do often make this distinction, even if it's not consistent across the marketplace.
"Hydrating" products tend to be those which seem to contain more water, or which contain ingredients that actively draw moisture into the hair or skin; humectants like glycerine or hyaluronic acid. You've probably noticed face mists or hair spritzes are frequently described as "hydrating", versus "moisturising" which is frequently used for richer, thicker products like creams.
Difference between moisture and hydration: skin
So how do these differences on the label feel when you use a product?
When it comes to your skin and scalp, products that claim to moisturise tend to be heavier on the emollient or occlusive ingredients. These ingredients are oilier and richer feeling, softening rough skin cells and making your skin feel smoother.
Products that claim to hydrate are usually the ones that plump up your skin. Again, they often include high levels of water and ingredients like glycerine or hyaluronic acid: humectants that draw water up from your dermis into your stratum corneum - the top layer of your skin.
A 'hydrating' or moisturising' product often depends on consumer perception. Image by Lumin.
This division is one of the reasons why beauty professionals tend to recommend using a serum (mostly plumping) and a moisturiser (mostly emollient and occlusive) so you get the best of both worlds.
But that doesn't mean there aren't plenty of products which claim to "moisturise" that have mainly a plumping effect, and others with "hydrate" on the label which cover your skin in emollients.
Remember, this name game is a marketing ploy: marketers are just going for the power of perception, so what evokes the mental picture of hydration will probably have "hydrating" in the name. It doesn't matter that hydrating is exactly what the overwhelming majority of skincare products do.
And since moisturising is also exactly what the overwhelming majority of skincare products do, there really is no concrete difference, moisture and hydration are one and the same.
Difference between moisture and hydration: hair
What about in hair products: is there a difference between products that claim to hydrate vs ones that claim to moisturise?
Not really, no.
Here as well, it's a matter of perception. In tests, consumers rated hair as "moisturised" when it was 'silky' or 'smooth', regardless of what the actual moisture content was. This conflation of moisture and softness is common in the natural hair sector; the idea of protein and moisture balance is a good example.
According to this concept, to maintain the right protein and moisture balance, you should alternate between protein and moisturizing treatments, modulating their use based on the reaction of your hair. If your hair starts to feel too stiff, it's because you've probably used too much protein. If it starts to feel too soft or too "moisturised", it's because you've used too much moisturizing conditioner.
The simplicity of this logic is very appealing. But it's a little too simple.
For one, proteins are moisturisers. Because of the way they help your hair attract and bind moisture, they are actually some of the most moisturising ingredients around.
Manufacturers often include protein in formulas for this very purpose, not just than the "protein filler" role we tend to think of, where protein is used to repair holes in a damaged cuticle. By the way, the fact that they do the filling also qualifies as moisturising, under the rejuvenating category, since this improves your hair's natural barriers, helping it retain moisture.
Proteins improve your skin and hair's barrier against moisture loss. Image by Amr Osman.
But for all the moisture they bring to your hair, proteins also tend to leave your hair stiffer. That's because they also increase your hair's elastic modulus: the natural stiffness that makes it resistant to breakage. To most people, that stiffness is not something they would associate with moisture, even though their hair's moisture content or hydration state has actually improved as a result of using these ingredients.
Instead, most people equate "moisture" with softness. It's why at the other end of the protein moisture balance, hair that is is overconditioned is seen as overly moisturised, even though the excess softness in those cases has less to do with moisture in the formula, than the effects of the cationic surfactants in the formulation, some of which are also used in fabric softeners to achieve the same effect.
While the idea behind a protein-moisture balance - that it's a good idea to use a mix of products that make your hair stiffer and products that make it softer - is solid, it's best not to take the wording too literally.
Hydration vs moisture: natural hair
So what does this mean when you're choosing the right hair products for your natural hair?
Should you not worry about whether a conditioner is "moisture" or "protein" when building your routine, since both of them can hydrate your hair? Can you moisture train your hair with protein conditioners?
In both cases, it depends.
If you're moisture training your hair because it feels dry and brittle, then you're trying to soften your hair. You can and should use protein - because if your hair is brittle that means it's breaking or about to break and proteins are a great way to stop that breakage right away.
Softening conditioners add flexibility to hair. Image by Adrian Linares.
But you should choose mainly softening conditioners, also known as "moisture treatments" because you want your hair to be more flexible, softer and smoother. This flexibility also helps fight breakage by making your hair less likely to snap when you bend, pull or twist it.
And because some of these moisture treatments which soften your hair actually contain protein, yes, you can use protein treatments to moisture train your hair. But remember, the most hydrating treatment--the one that adds the most moisture to your hair--might not be the one that softens your hair the most, because softening is only one type of moisturisation.
Case in point: La Aplanadora Treatment. It's a potent protein treatment based on keratin hydrolysates in a creamy, water-based emulsion that's dramatically strengthening - and also intensely hydrating.
When you apply it, you'll feel the moisture going all the way in; La Aplanadora's formula is easily the most penetrating Dominican conditioner we've reviewed, if not the most penetrating, period. By penetrating, we mean the treatment feels like more of its moisture gets distributed throughout your hair. This effect is especially noticeable on low porosity hair, which often struggles to absorb moisture from products.
La Aplanadora Treatment also has tons of slip, stretches out your roots and feels very silky when it's on your hair.
Once your hair is dry, however, it doesn't make your hair that soft. As a strengthening conditioner, and one that contains the type of protein that binds the strongest to your hair, it can make your hair feel a little on the stiff side. That stiffness is just your strand's elastic modulus - its resistance to breakage - getting that much stronger.
If you're actually seeking moisture, as in H2O, this treatment delivers moisture, deeper into the hair than other treatments. Since it also rebuilds the hair's structure, its moisturization effect is mainly in the rejuvenation and humectant categories.
If what you're looking for is softness though, you'll need to try a more emollient conditioner.
For that you could try another moisturising treatment: Halka Baba de Caracol. Baba de Caracol Treatment also happens to be a protein treatment; it contains collagen and elastin. But when layered over its matching conditioner it's also extremely softening, which balances out any of the stiffness from the proteins.
Like La Aplanadora, Baba de Caracol stretches the hair and adds tons of slip. It's also very softening even on extremely stiff hair. And it stays soft even after the hair dries. That's why it's often recommended as a moisture (as in softening) treatment, even though it contains proteins. The protein content doesn't get in the way. The Baba de Caracol Treatment duo does the job a moisture treatment is supposed to do; enhance moisture content, soften and smooth the hair.
So while moisture and hydration are one and the same, different formulas work differently to achieve the different roles moisture plays in your hair.
What Moisture (Or Hydration) Does For Your Hair
Call it water, moisture, hydration: for your hair, this one ingredient has two roles: it's a plasticiser which means it makes hair softer and smoother and it's also a strengthener, meaning it helps stop your hair from breaking (unless of course, you increase its levels excessively).
Different moisturizing ingredients, and the overall formulas they're included in will support different outcomes (humectancy, occlusion, rejuvenation/strength, or emolliency). The most obvious of these, in terms of how your hair feels, are softness and strength.
So when you choose your next treatment, think of which effect you need: softness or strength. Both La Aplanadora Treatment and Halka Baba de Caracol Treatment will hydrate/moisturise your hair. They just do it in different ways.
Choosing whether you want the dramatically stronger La Aplanadora effect or the dramatically softer Baba de Caracol effect is an easier way to get what you want.
Focusing on these end results is far more effective than agonising over whether a product is moisturising vs hydrating. Especially when you realise, there's no reliable difference between the two terms.
To add both the softness and strength aspects of moisture to your hair long term, you should think about moisture training your hair. You can use this FREE step-by-step moisture training guide to get you started.