It often happens in the search for new therapeutic agents that some old stand-by has been overlooked, whose luster has worn off, but which may have useful application in moments when the miracle drugs falter. In the world of topical therapy, urea is such a drug. Youthful skin with a visible glow – it’s the holy grail of skin care.
So, what if I told you the key to super-healthy skin is hydration?
Dehydrated skin causes horizontal lines to appear; the types of lines that lead to deep-seated wrinkles, especially if not treated correctly. That’s right; something as simple as keeping your skin plump and moist can ward off premature ageing for many years to come
But, shhh! There is one little “beauty secret” that not too many people know and that secret is Urea – which is, in my opinion, one of the most effective moisturising ingredients in cosmetic chemistry. Urea’s role within the skin is remarkable; it maintains a healthy moisture balance, bringing much-needed relief to dry skin, whilst keeping it soft, supple, and youthful.
It seems ironic to think that as far back as 1957, urea was viewed as an old, forgotten therapy despite being rediscovered by Dr Kligman, the man behind Retin A. And yet, even today there is very little information about what could be considered the holy grail of the skincare world.
So, What Is Urea?
Urea is a naturally-occurring substance found in the surface layer of our skin, and is an active part of our natural moisturising factor (NMF), which functions to keep skin hydrated, protected, and working efficiently.
It is made up of 40% amino acids, 12% sodium PCA, 9% glycerol, and 8.5% urea – all of which are water-binding (hygroscopic) components essential for maintaining the health, function, and hydration of the stratum corneum.
Healthy skin typically contains 28 micrograms of urea per square centimeter. Those with dehydrated and dry skin can see an improvement in their symptoms of as much as 50%, and in those with eczema, as much as 80%. There is evidence to suggest that urea helps treat ichthyosis, dermatitis, psoriasis, xerosis, and even nail fungus.
The Sciency Skin Bit
In order to understand how urea works, it is important to understand the skin’s structure.
Your outermost layer of the epidermis – the stratum corneum – is made up of corneocytes and an inter-cellular cement which has a high resistance to many chemical agents. Inside the corneocytes is our natural moisturising factor (NMF) – a mixture of substances that regulate the level of moisture on our skin’s surface by binding water molecules.
Urea is a natural component of our skin’s tissues and makes up 7% of our natural moisturising factor, which decreases with age.
Whilst applications of emollient and occlusive ingredients coat the skin’s surface to create instant moisturisation, it is only a temporary fix, which won’t improve the skin’s ability to create and hold water the way urea does. When it is applied to the skin, urea penetrates the stratum corneum, where it readily absorbs and retains water; increasing the capacity of the skin to hold moisture and rehydrate.
To conclude, it helps to regulate the cell cycle; encouraging natural desquamation or exfoliation, enhancing your barrier function, and regulating the good micro-flora that reside on your skin to keep your protective acid mantle intact.
“Urea appears to be a highly-active small molecule regulator of genes that impact keratinocyte differentiation, lipid synthesis and antimicrobial peptide production, together leading to improved permeability barrier function and likely antimicrobial defense as well.” (1)
Dry Skin Connection
Dry skin results from a lack of oil and water in the outer layer of skin, the epidermis. Skin becomes scaly, cracked, and itchy.
Moisture is normally retained in the epidermis by a surface film of oils (sebum), broken-down skin cells, and natural water-holding substances. Urea is one of these water-holding substances, the others being lactic and amino acids. We know reduced levels of urea leads to a lower water-binding capacity within the skin, which in turn leads to roughness, tightness, flaking, and irritation.
Research has found a link between severe dry skin conditions – such as ichthyosis, seborrheic dermatitis, psoriasis, eczema, and even nail fungus – and drastically reduced amounts of urea in the stratum corneum.
Urea stimulates the components of the skin that keep it healthy, which is referred to as epidermal gene expression. When applied, it increases the formation of filaggrin; an important protein found within the skin that keeps everything balanced. It also maintains the barrier function by building up your skin’s defence mechanisms.
Urea’s Skin-Loving Benefits
Meaning “water-loving”, this property gives urea its amazing ability to hold onto water molecules, keeping our skin moist.
Not only does it readily absorb water, but it also has a very high water content, which helps to reduce the amount of water lost through the skin.
On a molecular level, urea modifies the structure of amino chains and polypeptides within the skin, which is important for helping to moisturise our delicate tissues.
Research has found a direct correlation between our skin’s water content and its levels of amino acids. Basically, the more dehydrated and dry the skin is, the lower its share of dissolved amino acids.
To learn more about the damaging effects of dehydrated skin, follow the link.
Improves Barrier Function
One of the many ways urea benefits our skin is by helping to accelerate the cellular renewal process. The really great thing about this is that it strengthens the barrier function of the skin, helping to keep it youthful and healthy.
In the article, “Understanding the Acid Mantle“, I discuss the importance of having a strong barrier function and how it creates a stronger resistance against potential irritants.
Urea has powerful keratolytic properties that, combined with its hydrating properties, make it a potent moisturising and exfoliating treatment for the skin. It works in synergy with ingredients that create the molecular structure of healthy skin, such as lactic acid, helping other ingredients penetrate deeper.
Combined, these two ingredients actively work to remove dead skin cells and substances from the skin’s horny layer; improving cellular turnover in the epidermis and helping to dramatically improve the water-binding ability of the skin, literally REBUILDING HEALTHY SKIN from the inside out.
Urea further improves skin health by metabolising the antimicrobial peptide LL-37, which literally kills the acne-causing bacteria within the skin. An in vitro study also indicates that urea directly inhibits the yeast malassezia, which is often the cause of fungal acne.
Urea has another interesting profile; it can create a local anaesthetic effect on the skin and has anti-itch properties.
Studies have found that urea plays a key role in increasing the permeability of certain skin care ingredients, working as a vehicle for other performance ingredients by encouraging them to penetrate the epidermis easily.
Dry skin is often due to a reduction of urea in the skin’s delicate tissues, leading to tightness and flakiness. Because urea is a natural moisturising factor, it can offer instant relief to dry skin.
I include urea in H₂O Hydrating Complex to help hydrate and repair skin cells.
The gentle exfoliating action of urea helps to leave the skin super smooth, especially when layered; the texture of the skin is visibly softer, giving it a youthful glow. I have seen some great results from urea on my clients who suffer from extremely dry and dehydrated skin.
Urea’s Best Bits
Phew! With so many beautifying properties, where do you begin?
For the benefit of those who require a little recap, here are this cool little ingredient’s best bits:
- Urea is naturally produced by our skin
- It regulates our skin’s moisture content and is an essential component of our Natural Moisturising Factor (NMF)
- Urea is hygroscopic, which means it is able to bind moisture on to the outermost layer of our skin
- The perfect treatment for dry skin, it has anti-itch and anti-microbial properties
- It can kill the bacteria cause acne
- It is also keratolytic, meaning it breaks down the connections between dead skin cells; naturally exfoliating the skin and helping ingredients penetrate further
Percentages used in skin care
- Less than 10% in a formula helps with water retention in the skin, helping to bind moisture onto the skin. This is due to its extremely hydrophilic nature, making it a popular choice for its moisturising effect.
- Over 10% urea has a light keratolytic effect, making it a great choice for those with dry, flaky skin that requires an extra boost. At this percentage, it creates an exfoliating product that won’t scratch the skin, perfect for those with conditions such as eczema.
- At higher doses of around 30-40%, its strong keratolytic properties make it great for more serious therapeutic uses, such as treating psoriasis.
The Naked Truth
Urea is often referred to as Carbamide, the primary organic solid of urine, which is waste that has been produced by the body after it metabolises protein.
Thankfully, the urea used in the cosmetic industry is made from synthetic sources and is not animal-derived. It is formed from ammonia and carbon dioxide, and can be produced in either a solid or liquid form.
There are three forms of urea found in personal care products: Hydroxyethyl Urea, Diazolidinyl Urea, and Imidazolidinyl Urea. People often get confused by these, but they are, in fact, completely different ingredients.
Diazolidinyl and Imidazolidinyl Urea are antimicrobial preservatives used in the skincare industry to protect personal care products from bacteria, yeast, and mold. They do get a lot of bad press as a preservative due to the fact that they are proven to release formaldehyde. Hydrovance (INCI name “Hydroxyethyl Urea”) is a potent humectant and considered safe as a cosmetic ingredient.
I do hope I have gone some way to answer your questions on what urea is. I appreciate that dry skin is a really frustrating skin type to treat, simply because it causes so many conditions within the skin:
- Dehydration due to a lack of water
- A lack of a protein called Fillagrin
- Dryness due to a reduction in ceramides and moisturising lipids