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Many of us use moisturiser on a daily basis, perhaps even mindlessly….because, well, that’s what we’ve been brought up to know. But, do we actually need moisturiser? This post will explore the science behind moisturisers to see if they actually do anything for our skin.
Setting the record straight
First off, let’s set some records straight. Let’s start with our terminology – ‘dry’ and ‘dehydrated’ skin might appear to describe the same skin condition, but are actually quite separate skin states.
The main difference between these skin descriptions (dry skin is often classified as a skin type and dehydrated skin is often stated as a skin condition) is that ‘dry’ skin lacks oil and ‘dehydrated’ skin lacks water.
Dry skin characteristics and causes
Dry skin is frequently linked with a damaged skin barrier function. This impaired barrier function triggers cytokine generation and secretion, which can lead to skin inflammation, increased proliferation of keratinocytes and epidermal hyperplasia.
The mains characteristics of dry skin include:
- Skin feels tight (especially after cleansing)
- Skin may feel rough
- Flaky skin
Causes:
- Genetic predisposition towards this skin type
- Harsh cleansers/soaps
- Medications
- Hormones
Dehydrated skin characteristics and causes
The ability of the skin to hold water is related to the stratum corneum (SC) – the outermost layer of the epidermis – which acts as a barrier to water loss. Signs of dry skin (flaky skin) begin to appear when SC water content falls below 10%.
The main characteristics of dehydrated skin include:
- Highlights fine lines
- Possible patchy foundation as the skin tries to absorb the moisture from the foundation
- Skin can also feel tight
- Dullness
- Can also have flaky skin
Causes:
- The sun – studies suggest that sunlight exposure decreases stratum corneum water content
- Low humidity and windy conditions – ie the winter time can accelerate the loss of water through the skin
- Hot showers and central heating – hot showers and central heating can also contribute to skin dehydration
- Ageing – ageing skin often struggles to keep moisture levels high
Moisturisers intended use
So, are moisturisers meant for dry or dehydrated skin? Well, the good news is, we can target both – different moisturisers provide different benefits.
Moisturiser for dry skin
The depletion or disturbance of the major lipids in the SC (due to genetic predisposition, soap, dry air and age) is thought to be one of the factors producing dryness and barrier disruption in skin conditions. The loss of SC lipids may be associated with eczema and dry skin in general. The SC lipids consist of a mixture of ceramides (45–50% by weight), cholesterol (20–25%), and free fatty acids (10–15%).
So, if you have naturally dry skin or dry skin as a result of a cleanser stripping away your natural oils then you are going to want to look to replace the skin’s lipids.
Since ceramides make up most of our SC lipids it would seem logical that topical application of ceramides would repair the skin barrier. However, studies have shown that when ceramides, cholesterol or free fatty acids are applied alone they aggravate the barrier further. A study found a mixture of ceramides, cholesterol and free fatty acids in appropriate molar ratios (the free acids being either linoleic acid, palmitic or stearic acids) allows for barrier repair.
Another study found that a lipid mixture containing cholesterol, ceramides, palmitate and linoleate (4.3:2.3:1:1.8) enhanced the barrier function significantly after the barrier function had been disrupted via the extraction of lipids.
So, for those with dry skin try to look for moisturises containing ceramides, cholesterol and free fatty acids (either linoleic acid, palmitic or stearic acids), but also, since dehydrated and dry skin go hand in hand, look out for ingredients discussed below for dehydrated skin.
Moisturiser for dehydrated skin
For dehydrated skin we are going to want primarily two things from our moisturiser: 1) a moisturiser which decreases transepidermal water loss from our skin (occlusives are good for this) and 2) a moisturiser that is going to reintroduce water back into our skin (humectants are good for this).
What are occlusives: Occlusives seal in moisture and stop water from evaporating. They do this by forming a hydrophobic layer on the surface of the skin. And quick tip – applying moisturiser when the skin is still damp helps to lock in extra moisture.
If you’ve ever wondered what the difference is between emollients and occlusives – emollients often provide some occlusive properties, but the main function of emollients is to help soften the skin. Emollients are typically more light-weight.
Common occlusives include: petrolatum, dimethicone, lanolin and mineral oil.
What are humectants: humectants increase the water content of the skin by enhancing water absorption from the dermis into the epidermis. It is also possible that humectants are able to draw in water from the external environment (depending on the environment). Humectants work since they contain hydrophilic groups which make them attracted to water molecules.
Common humectants include: glycerin, hyaluronic acid, sodium hyaluronate and urea.
Top moisturiser picks
Dry skin
Bioderma Atoderm Intensive Balm
This balm contains “an exclusive Lipigenium complex composed of bio lipids and ceramides” and is said to work well for extremely dry, irritated, or eczema-prone skin.
Skinceuticals Triple Lipid Restore 2:4:2
A pricey option, but for good reason – this patented ratio of ceramides, cholesterol and fatty acids will be sure to repair that barrier function.
Avène XeraCalm A.D. Lipid-Replenishing Cream
This cream is excellent for dry skin – containing Cer-Omega lipids, (Omega 6 fatty acids, Ceramides and Sterols (plant-based cholesterol)) this cream helps to repair the skin’s barrier.
Dehydrated skin
Formulated with 41% Petrolatum, aquaphor performs as a great occlusive. In addition, studies have found aquaphor to be clinically effective in treating mild-to-moderate atopic dermatitis. Petrolatum can also help restore the stratum corneum barrier by initiating the production of intercellular lipids, including free sterols, sphingolipids, and free fatty acids. So it’s good for dry skin too.
BeautyStat Universal Pro-Bio Moisture Boost Cream
This fragrance-free cream should work wonders for thirsty skin – this cream includes a generous amount of hyaluronic acid, providing the skin with an immediate moisture boost, whilst simultaneously mending your skin barrier through the use of pomegranate sterols and ceramides, decreasing transepidermal water loss, keeping the newly introduced moisture locked in.
La Roche-Posay Hyalu B5 Pure Hyaluronic Acid Serum
This hydrating serum contains two different sized molecules of Hyaluronic Acid. The larger sized hyaluronic acid works at the surface of the skin to reduce wrinkles and re-plump the skin. Whilst the smaller molecule penetrates more deeply into the skin to increase skin volume. The serum also contains other actives; the presence of vitamin B5 helps with the natural skin repairing process and helps to repair damaged skin, whilst madecassoside helps stimulate collagen synthesis.
Key takeaways
- ‘Dry’ and ‘dehydrated’ skin are different.
- Look for moisturisers containing humectants, occlusives and emollients for a triple whammy, targeting both dry and dehydrated skin.
- Whatever you do, try and exfoliate occasionally since removal of dead skin cells will allow moisturiser to better penetrate our skin.
References
Kasolang, S., Adlina, W. A., Rahman, N. A., & Nik, N. R. (2020). Common skin disorders: a review. Jurnal Tribologi, 25, 59-82.
Liu, Z., Fluhr, J. W., Song, S. P., Sun, Z., Wang, H., Shi, Y. J., Elias, P. M., & Man, M. Q. (2010). Sun-induced changes in stratum corneum function are gender and dose dependent in a Chinese population. Skin pharmacology and physiology, 23(6), 313–319.
Verdier-Sévrain, S., & Bonté, F. (2007). Skin hydration: a review on its molecular mechanisms. Journal of cosmetic dermatology, 6(2), 75–82.
Sahle, F. F., Gebre-Mariam, T., Dobner, B., Wohlrab, J., & Neubert, R. H. (2015). Skin diseases associated with the depletion of stratum corneum lipids and stratum corneum lipid substitution therapy. Skin pharmacology and physiology, 28(1), 42-55.
Mao-Qiang, M., Feingold, K. R., Thornfeldt, C. R., & Elias, P. M. (1996). Optimization of physiological lipid mixtures for barrier repair. Journal of Investigative Dermatology, 106(5), 1096-1101.
Yang, L., MAO‐QlANG, M., Taljebini, M., Elias, P. M., & Feingold, K. R. (1995). Topical stratum corneum lipids accelerate barrier repair after tape stripping, solvent treatment and some but not all types of detergent treatment. British Journal of Dermatology, 133(5), 679-685.
