Date: October 2007
Does 70% rubbing alchol completly evaporate ? or does it
leave any residue why would it need to be rinsed off???
70% of it is isopropyl alcohol. The other 30% is water.
Alcohol and water can both evaporate completely,
leaving no residue, if there are no solids dissolved in them.
Having little or no such solids is certainly one of the main requirements
for bottling drugstore grade "rubbing alcohol".
So, no, I see no distinct reason to rinse after briefly wiping
one's skin with rubbing alcohol.
But individuals may have fuzzy self-determined reasons.
For example, alcohol de-greases your skin somewhat,
though not as badly as acetone does.
Some people might feel their skin feels more natural, less dried,
if they rinse & dry after swabbing with rubbing alcohol.
It adds water and possibly redistributes remaining skin oils,
and maybe has less of the whitish look of dried dead skin fragments.
Try dabbing a spot on your fore-arm with acetone
and see if the skin looks dried, whiter.
That appearance and feel might be a clue
why some people would prefer to rinse after alcohol.
Y'know, I still don't know what purpose and manner of
exposure to alcohol you are referring to,
whether for sterilization or fever-cooling
or accidental spills or many other possibilities...
The alcohol in "rubbing alcohol", chemically isopropanol, will leave a
small residue at 25 C. However, for all practical purposes the increase at
body temperature, about 37 C. will ensure that the alcohol will evaporate.
There is no need to "rinse it off". In fact, doing so could introduce
pathogens that would be a greater risk than any residual isopropanol.
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Update: June 2012