<<Disclaimer: Verify this information before applying it to your situation.>>
 
Again, thank you to those of you who helped me out on this.  I
appreciate the time you took!!  Below is a summary of the replies I
received.
 
Douglas in Pittsburgh:
 
Balsamic vinegar is a wine vinegar aged in wooden barrels. It is
often sulfited and there is some concern that caramel color may be
added. This concern is raised possibly from the tannins from the
wooden barrels. Some people get bad headaches. Whether the barrels
had been previously used for another product such as brandies could
be a problem. Or the sulfites may bother you if you are an asthmatic.
 
 My thought is that wine vinegar is probably safer.
 
Bob:
 
Balsamic vinegar is made from unfermented grape juice so it is not a
 
wine vinegar nor a grain vinegar either. There are many different
grades of balsamic vinegar but all should be gluten free. I gathered
 
this information from watching "The Frugal Gourmet" which had an
entire show devoted to this.
 
George & Gayle:
 
Everything I've read on the list about balsamic vinegar indicates
that it is not a problem. Good Greek or Italian olive oil and
balsamic vinegar makes any salad a treat in our house.  You should
try to get the kind that has the letter API on the label.  It means
it is made by a family that is a member of a consortium, and is 16%
traditional balsamic and at least 18 months old. Monari Federzoni
with a green label, is the most common brand in gourmet shops. This
is at least three years old. It has 25% traditional balsamic vinegar
 
(which is made with must - the juice of local grapes aged in stacks
of barrels like sherry. (If you have an allergy to mold spore you may
 
want to try a little at first and wait a day or two to see if it
causes a reaction). Commercial balsamic vinegar is produced in the
Modena area of Italy.  It contains no balsam, but got the name
because it was believed to be magically medicinal, like balsam. Black
 
label Federzoni is 8 years old and 45% traditional - as much as $20 a
 
quarter liter bottle. Mazzetti comes in a straw wrapped bottle -
smoother and sweeter. Bellilno brand is less than $3 a bottle.
Colavita makes a balsamic vinegar which is very sweet-sour and
somewhat cheaper. It does not have API on the label.
 
Marvin in Florida:
 
Balsamic vinegar: Acetic acid = 6%. Made in Modena. Balsamic vinegar
 
is made from either Lambrusco, Trebbiano, and or Sangiovese.  The
vinegar is aged a minimum of 12 years. The grapes are pressed and
reduced to 1/2 to 1/3 to create Saba which is used in fermentation
that produces the tart=sweet taste. The wine is then stored in wood
barrels: i.e.: oak, chestnut, cherry, ash, mulberry, apple, or
juniper. Different woods create different undertones. The first
barrels contain 60 liters each and are stored in a warm area with a
vented cover for evaporation. As the barrels are evaporatng they are
 
periodically topped with with the remaining mature vinegar. Another
brand of balsamic vinegar is made from Trebbiano grapes. The juice is
 
then heated and aged in barrels evaporating and concentrating in
flavor. Well aged balsamic vinegar is deep rich  brown with a sweet
and sour flavor. Most balsamic vinegars found in the U.S. are not
"aceto balsamico tradizionale" but unaged balsamic vinegar. These
vinegars lack in body and flavor that the well aged possess, yet have
 
a fair sweet and sour balance flavor not found in any other vinegars.
 
Diana