I use Allegra every day but in the past have also gotten pretty good
relief from Zyrtec.  I've also noticed that sometimes there is something
in the air for a week or two that Allegra doesn't seem to handle very
well.

After mentioning all this to my doctor he suggested switching to Zyrtec
once in a while because the literal suggests that one's body might
respond better to Allegra if periodically given a break from it.  (I
don't know if this is true for all antihistamines or just Allegra.)

Is there a standard protocol for doing such a thing, e.g., use another
medicine for 2 weeks every 6 months?  I tried being off Allegra once for
a week - I had to because of then-pending allergy test - and was pretty
miserable.  I don't think going with no antihistamine for any length of
time is best for me unless there's a compelling reason.  (I have severe
allergies to several very common things - dust mites, mold, grass among
others - and do very well in a HEPA-filtered environment but go to
client sites pretty regularly so I'm in unfiltered air for 8-16 hours
per day sometimes.)

Thanks in advance.

-S-