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Now you’re just rubbing it in: How washing your hands can harm you

Courtesy Story

Could washing your hands be harmful to your health? Surprisingly, yes, if you were exposed to a chemical warfare agent. The soap and water mixture, combined with the rubbing motion of washing your hands, could enhance the chemical penetration through your skin.

After a hundred years of research, why does protection from persistent chemical warfare agent exposure and skin decontamination remain so difficult? In part because a detailed mechanistic understanding of how agents are absorbed through the skin, specifically the stratum corneum (SC), has been a challenge to accurately determine.

However, new research managed by the Defense Threat Reduction Agency’s Joint Science and Technology Office is working to enhance decontamination processes for the warfighter.

Until the 1970’s, the SC, the outermost layer of the five layers of skin, was thought to be inert, like a thin plastic sheet whose role was to protect the more active lower layers of the epidermis.

It has only been within the last five years that scientists have uncovered new information regarding the intricacy and complexity of the chemical and biological structure and function of the SC.

Understanding these functions, in particular SC diffusion mechanisms and measuring dermal absorption rates, is critical to developing capabilities that protect warfighters from toxic agent exposures.

A team, including principal investigator Xiaoying Hui at the University of California, San Francisco, managed by Dr. Brian Pate from the DTRA Research and Development Directorate, is leading the global effort to provide state of the art data, information and knowledge relative to the development of new dermal protection, detection and decontamination countermeasures and capabilities. Recently this team performed a review from a biological and clinical perspective to obtain additional sources of data that will help guide current DoDrelevant research in this area.

Key findings reinforce the theories that there are multiple layers of SC structural heterogeneity that result in unique substance partitioning characteristics across these membranes. It is this partitioning that has thwarted previous attempts to accurately model and understand the absorption rates and diffusion mechanisms within the SC.

The team also found that the risks and weaknesses of standard decontamination methods that utilize water and detergent include the lack of clinical evidence necessary to validate their efficacy. Risks of detergents that can remove skin lipids are still under investigation because detergents may impair or hinder decontamination by altering the natural inherent SC membrane protective capability and allow for faster toxin penetration into the sub SC layers of the skin.

Alternate in vitro methods are needed due to challenges pertaining to efficiency, cost-effectiveness and ethical concerns of certain in vivo experiments.

This is important, in part, because the SC holding capacity (i.e., reservoir) of topically-applied chemicals and the relationship between the interaction of the chemicals’ physicochemical properties and SC components remain unclear.

The team’s strategic use of an approach toward dermal decontamination that focuses on characterizing the human SC will lead to an improved understanding of the mechanisms involved and thereby enable new dermal protection and mitigation capabilities for warfighters.

The full article can be found in the Journal of Applied Toxicology article titled “Recent knowledge: Concepts of dermal absorption in relation to skin decontamination.”

POC: Dr. Brian Pate, brian.d.pate.civ@mail.mil

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