Typically, there is only a minute amount of the alcohol in hand sanitizers that is actually absorbed through the skin. However, most doctors recommend that the usage of these are only done when soap and water is not available due to, as you stated, the lack of long term studies at this point on the topic. However, if hands need to be sanitized and there is not soap and water present, then the usage of a hand sanitizer is far safer than not using anything to clean the hands.
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thank you for your reply. according to fick's law ethanol applied to the skin could actually reach some toxic levels if the area is large enough and prolonged exposure. are you aware of any articles that discuss prolonged exposure?