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Jots and Thoughts

The musings and notes of the Threla team about body and skincare products.

Lotions and Skin Moisturization

Threla LLC - Friday, April 24, 2009

Skin is our barrier to the external environment, preventing water loss and preventing the ingress of unwanted germs and chemicals. A robust barrier function is dependent on the proper structure and composition of skin’s outermost layer known as the stratum corneum. In healthy skin, the intercellular matrix within the stratum corneum is composed primarily of highly structured lipid layers, which provide a physical barrier against water loss. Additionally, the healthy stratum corneum contains high concentrations of Natural Moisturizing Factors (NMF), which are natural humectants that help the skin bind and retain water. Perturbations to the lipid barrier structure or the NMF level by the environment, which lead to the loss of water from the skin, are the main causes of many dry skin conditions. Therefore, the most effective treatment for dry skin is moisturization.

 

A good moisturizer should employ a combination of ingredients intended to reduce water loss from the skin and to repair the damaged lipid barrier. Occlusive agents in the moisturizers form a film that physically reduces the evaporation of water from the skin, thereby increasing the skin water content. Examples of occlusive agents include vegetable oils, such as coconut oil and shea butter, and synthetic ones such as silicones. Humectants help the skin bind and retain water, mimicking the role of the NMF. Examples include glycerin and alpha hydroxy acids. Barrier-repairing agents like lipids and lipid synthesis enhancers facilitate the repair of lipid bilayers and improve the stratum corneum barrier function.

 

Based on these principles, our lotions are formulated with:

  • natural oils rich in essential fatty acids to provide emollience, building blocks for lipid synthesis, as well as occlusion against water loss
  • the components of NMF - lactic acid, urea, and sodium PCA – to keep the skin hydrated
  • a lower pH to emulate the natural pH of skin, which is ~4.7 
Moisturizers may also contain a host of other ingredients such as ingredients to boost collagen production and encourage cell turnover.  However, many of these claims are unproven. Our take is to create lotions that do what they are supposed to do, i.e. moisturize and prevent dry skin, rather than promote hope in a jar.

References:
Harding C.R. et al.  Dry skin, moisturization and corneodesmolysis.  Int. J. Cosmet. Sci. 22 21-52 (2000)
Rawlings A.V.  Trends in stratum corneum research and the management of dry skin conditions.  Int. J. Cosmet. Sci. 25 63-95 (2003)

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