FJ,

Do you have any neck pain? Headaches at the BACK of the head?

There is a relationship between the cervical spine function and
dizziness. The condition is called cervicogenic vertigo (CV), meaning
vertigo emanating from a neck-related cause. Your problem may be
vestibular/labyrinthine in nature, esp. if antihistamines "seem" to
work. But you may have two concurrent, yet unrelated problems
(sinusitis and cervicogenic vertigo). If you do have CV, a
chiropractor may be of help. (Disclosure: I am a chiropractor.)

There is a diagnostic way of determining which condition exists. You
sit on a swivel stool and the doctor stands behind you, holding your
head gently on either side. First, you swivel your body side to side
while your head remains looking forward. If vertigo is reproduced via
this method, then it is likely CV, since the neck is rotating but not
the head (and labyrinthine system). Next, the body remains still while
you or the doctor rotates your head to each side. If dizziness appears
here, with both the neck and head moving, then the vertigo likely has
a vestibular cause.

Of course there are other tests that can be done, and if you have
other symptoms a visit to a neurologist may be in order.  Otherwise, a
trial of spinal manipulation may benefit you.

FJ,

Do you have any neck pain? Headaches at the BACK of the head?

There is a relationship between the cervical spine function and
dizziness. The condition is called cervicogenic vertigo (CV), meaning
vertigo emanating from a neck-related cause. Your problem may be
vestibular/labyrinthine in nature, esp. if antihistamines "seem" to
work. But you may have two concurrent, yet unrelated problems
(sinusitis and cervicogenic vertigo). If you do have CV, a
chiropractor may be of help. (Disclosure: I am a chiropractor.)

There is a diagnostic way of determining which condition exists. You
sit on a swivel stool and the doctor stands behind you, holding your
head gently on either side. First, you swivel your body side to side
while your head remains looking forward. If vertigo is reproduced via
this method, then it is likely CV, since the neck is rotating but not
the head (and labyrinthine system). Next, the body remains still while
you or the doctor rotates your head to each side. If dizziness appears
here, with both the neck and head moving, then the vertigo likely has
a vestibular cause.

Of course there are other tests that can be done, and if you have
other symptoms a visit to a neurologist may be in order.  Otherwise, a
trial of spinal manipulation may benefit you.