I've heard over and over that people who do low carb find their
allergies leave. Same story with people who start diet meds. Absent
any other relevant theories, I wouldn't be surprised if the allergy
relief is partly due to not having food allergens in your diet (of
things you probably didn't know you were allergic or sensitive to).
The other thing I'd personallys suspect is that your insulin response
is changed for the better.  There's some theory to suggest improving
body heat (if you run cold) might help alleviate allergies.

As to why allergies come back, my bet generally would be those lovely
counterregulatory systems we all have... ie you make a change, for
awhile the change remains in effect, but then your body recognizes the
change and tries to homeostatically get back to where it was before--
and through one of these myriad mechanisms, your allergies return.
That's why I'm for gradual changes rather than system shocks... for
instance if one's on a low carb diet-- I'm leery of staying TOO far
into ketosis for fear my *incredibly efficient* body will adjust.

Donna

_________________________________________________________
DO YOU YAHOO!?
Get your free @yahoo.com address at http://mail.yahoo.com