Date: Thu, 22 Apr 2010 08:50:40 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Ralph Stuart <secretary**At_Symbol_Here**DCHAS.ORG>
Subject: Re: Hand sanitizer

From: McGrath Edward J <Edward.McGrath**At_Symbol_Here**redclay.k1>
Date: April 22, 2010 8:47:05 AM EDT
Subject: RE: [DCHAS-L] Hand sanitizer

The benefit of 70 % isopropyl alcohol over 99 % is that from a microbiological viewpoint, 70 % IPA is more penetrating to bacteria.  Any surface disinfectant should remain in contact with the surface for 30-60 seconds before being wiped away (check the directions on a bottle of 409).  A 70 % solution seems to work better under this protocol.


The real benefit of hand sanitizer is that because it is non-specific, bacteria, fungi, and viruses are unlikely to become resistant to the effects (compare this to the issues with antimicrobic hand soap or antibiotics).  The thing to remember is that disinfection is not the same as cleaning.  If your hands are grimy (and many of our students in K-12 situations have dirty hands), the alcohol gel will kill microbes where it contacts, but their hands will stay dirty.  Furthermore, one of the primary reasons hand washing cuts down on transmission of infection is the physical act of washing and using soap.  To that end, plain old Ivory Soap will reduce infection transmission when used properly.


The moral of the story=97alcohol gel is helpful for disinfection but not for cleaning.  If I can, I generally wash my hands after a lab experience.  Fifteen seconds (the =93happy birthday=94 rule) is enough.  Just the same, I carry a small bottle of alcohol gel for situations where hand washing is inconvenient.


Edward J. McGrath
Science Supervisor
Red Clay Consolidated School District


office:  (302) 552-3768

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