crying (from grief) mimics many of the symptoms of an allergic
reaction (redness, swelling, tearing, runny nose), is this just coincidence?

tesla8...

Possibly not. There are many wholistic practitioners who see
the similarity and consider that, in some cases at least, the
presence of allergic symptoms may indicate the efforts of a 
suppressed emotion attempting to make its way to the surface,
but being resisted by the intellect or the ego. In those cases
the symptoms might be relieved if the person allowed themselves
to have a good cry about what's eating at them.

sublime1-ga

an allergy is defined as the body's unfavourable reaction to some
external entity. so going by the technicality of this
definition.......YES crying can be defined as an "allergic reaction"
(so to speak). since medical science says that our body can be
allergic to anything under the sun (including the sun itself) we can
say that crying is an allergic reaction.

On the contrary the symptoms outlined like redness,swelling,tearing
cannot be the exclusive criterion to classify crying as an
allergy.this is because the responses of the body to allergies can
count upto thousands.an interesting example : erection in males is
characterised by swelling and reddening. so going by your list would
you classify that as an allergy ???? (now we are thinking ) right?? so
now you have it ...

another line of thought : most allergies are treatable with medication
like anti histamines etc etc. now to find a medication which stops
crying ?? (that would be amazing)but hasnt happened.so ill say crying
is no allergy. go ahead CRY IT OUT.

Also, regarding tears specifically, tears have different chemical
compositions. Allergy tears are different than emotional tears - with
the emotional tears containing more serotonin.
Google book reference:

http://books.google.com/books?id=8ibwNs7QEm8C&dq=chemical+composition+of+tears&oi=print&pg=PA7&sig=tXyHMlRowuqsmsahfN4jZgM7738&prev=://www.google.com/search%3Fhl%3Den%26q%3Dchemical%2Bcomposition%2Bof%2Btears%26spell%3D1