Primarily produced from the metabolism of dietary protein and other organic nitrogen compounds in the liver, urea or carbamide is excreted in the urine and sweat as a waste product. Urea is also commonly used in skin care products for more than a century due to its proven benefits. Though you may be thinking, who on earth would want to rub urine component on their skin? Well, actually, urea is also an important naturally occurring component of the skin epidermis that helps absorb moisture.
Interestingly, the practice of urotherapy, using one’s own urine for an aesthetic purpose can be dated back to the Aztecs and ancient Egyptians. Thankfully, contrary to your worst nightmare, skin care formulations that contain urea include synthetic-made urea, produced from ammonia and carbon dioxide in laboratories, not the one excreted from the human body.
Below are some reasons why urea is commonly used as important ingredients in many skin care formulation, especially for dry and sensitive skin:
A natural moisturizing factor of the skin
The stratum corneum, the outermost layer of the skin, protects the body from external agents and controls exchanges with the environment. The presence of moisture attracting molecules, known collectively as Natural Moisturizing Factor (NMF), allow the stratum corneum to retain water, thus keeping the epidermis moisturized and elastic.
Urea is one of the components of the NMF that contributes to the preservation of healthy skin hydration levels. A decrease in NMF levels induces loss of water in the stratum cornea and reduces epidermal elasticity. In healthy stratum corneum, urea corresponds to 7% of the NMF, a percentage that decreases with age.
Preserve skin hydration
Whilst applications of emollient and occlusive ingredients coat the surface of the skin creating instant moisturisation, it is only a temporary fix and won’t improve the skins ability to create and hold water. Urea, on the other hand, penetrates the stratum corneum, where it readily absorbs and retains water. This increase the capacity of the skin to hold moisture and rehydrate, making urea a powerful humectant.
Common skin problems characterized by dry skin such as eczema, psoriasis, and ichthyosis vulgaris are all characterized by an inability of the stratum corneum to maintain hydration and epidermal barrier dysfunction manifested as patches of rough, scaly, or hyperkeratotic skin.
Improves skin integrity and barrier function
Healthy skin is characterized by efficient control of water loss that allows the maintenance of a good level of hydration, and consequently, a strong physical and chemical barrier. Urea regulates transepidermal water loss and restores the ability of the stratum corneum to attract and maintain hydration.
Urea also works both on the external and cellular level. It is known to accelerate the skins cellular renewal process by stimulating epidermal gene expression. This help skin cells form a protective barrier and strengthen its barrier function, keeping the skin youthful and healthy. Not only limited to treatment, routine use of a urea moisturizer also prevents progression of dry skin before it occurs.
A rare feature of urea that made it a superb therapeutic agent for the skin is the fact that it can act both as a moisturizer and a gentle exfoliator. At lower doses (less than 10%), urea-containing topical formulations act as a skin moisturizer, while at higher concentrations (more than 10% urea), urea-based preparations exert a keratolytic action.
Keratolytic action means that urea can exfoliate and soften keratin, a key component of skin. By dissolving the horny substance holding the top layer of skin cells together, urea helps the dead skin cells fall off as the skin retains water. This action ultimately improves the skin’s moisture-binding capacity. This also means that high concentration urea can be used to treat hyperkeratotic skin conditions.
Urea is also useful in combination therapies with anti-inflammatory and anti-fungal drugs, due to its activity as a penetration enhancer. Urea facilitates the crossing of the skin barrier by other molecules and thus, improves the effects of drugs used in combination therapies. Skin penetration of topical medication such as corticosteroids and antifungals can be facilitated by urea to treat scaling and inflammation of the skin.
No adverse effect
Most clinical studies involving urea formulation as cream, emulsion, or foam, with urea concentrations of 10% reported no adverse events, confirming the safety of use of topical urea formulations.
Restoring stratum corneum barrier integrity and function is a universal goal in the treatment of a multitude of skin diseases and conditions. Psoriasis and eczema sufferers are discovered to have a deficiency in urea. Skin with psoriasis has 40% less urea than healthy skin while eczematous skin lacks 85% of the urea it needs.
This explains why urea remains one of the oldest and yet one of the most beneficial ingredients in skin care formulation despite the continuous discovery of novel skin care ingredients and innovative formulations.
Hello Health Group does not provide medical advice, diagnosis or treatment.
Review Date: March 6, 2019 | Last Modified: November 29, 2019
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