When I splash on after shave it hurts for a few seconds and then the
pain goes away.
Further applications of after shave don't hurt at all. What happens to
the skin which causes the pain in the first place and what happens to
the skin which causes the pain to go away and not come back (until the
next shave)?

Optional bonus question: why is after shave two words and not one?

Hi mxnmatch


Many after shaves contain alcohol, which possesses antibacterial
abilities, helping to prevent infections of nicks or shaving cuts.

Now while alcohol has antiseptic, antimicrobial and bacteriostatic
properties, it also works as a local anesthetic.  After the initial
sting of the alcohol, the nerves in the surface of the skin are
anesthetized enough to eliminate the sting from repeated applications.

As for why there is pain in the first place, you just wounded your
face.

When you apply alcohol several hours after shaving, you should feel no
sting.  Alcohol on healed skin will have a cooling rather than a
stinging effect.  When we shave (and I am presuming a blade razor
rather than electric) we remove protective skin cells down almost to
the level of living tissue.  When we apply an alcohol containing after
shave, the protective layer of old skin cells is so thin, it allows
the alcohol to penetrate to living cells, thus the sting.  Alcohol
stings "wounds" plain and simple.  And though the layer of skin we
removed constitutes only the most minor (except for nicks) type of
wound, the alcohol reacts with the living cells it touches in exactly
the same way.

After a few hours, the skin on the face has returned to a healed over
condition and newly applied alcohol should not sting until we perform
our ritual of self mutilation again the next day.

So, that is "What happens to the skin which causes the pain in the
first place and what happens to the skin which causes the pain to go
away and not come back..."
_____________

Optional bonus question: why is after shave two words and not one?

When I went searching for "after shaves effects +on skin,"  a certain
unnamed, but very easily guessed search resource asked : "Did you
mean:aftershaves effects on skin."

You need to ask that question of a far higher power.
_____________

If I can clarify anything before you rate the answer, please ask.

Search - Google
Terms - alcohol +and skin, after shaves, aftershaves, aftershave
astringents, astringent effects, alcohol +and wounds

The websites found were mostly commercial in nature but a lot of
information can be gleaned from them.

Commercial page of MenEssentials.com
( http://www.menessentials.com/brands/cn/about_cn.html ) - the section
about aftershaves provides some 'formulation' information as part of
product description.

This page from Zila Pharmaceuticals deals with the 'stinging' of a
topical medication containing alcohol.  It also explains how the
stinging can be stopped with an application of ice prior to the
alcohol.  This relates back to the statement about "anesthetized" skin
not feeling the application of alcohol.
( http://www.zila.com/pages/zila_prof_pharm/index_prof.shtml )

A page which contains information about topical treatments containing
alcohol and the stinging effects.  From "Pharmacy Business and
Practice"
( http://www.atalink.co.uk/npa/html/p304.htm )

Here is a PDF format report on the effects of alcohol contact with the
skin from Chemtronics Inc.  while the report deals with emergency
situations, there is good information.
( http://www.precision.com/MDS%20Sheets/Chemtronics/cs25.pdf ) 

Cheers
digsalot

Excellent! A much more thorough answer than I was expecting for just
$5. My curiosity is sated. Actually, I'm finding answers.google.com to
be somewhat addictive.