Subject: why does chewing gum help equate pressure on the ear during a plane flight?

The way the eustachian tube helps is when the air pressure outside changes, the
air pressure inside the ear has to adjust via the tube. 
The way the air adjusts is through a transfer of air through the eustachian tube
that goes to the back of the nose. That tube allows air to get in and out of the
middle ear as needed to adjust for pressure changes. When you're on an airplane
and you undergo a rapid pressure change, that tube needs to work a little harder
and a little more rapidly than it normally would.How would chewing gum or
swallowing help this? Is it stopping the eustachian tube from adjusting the air
fast? But then that would be bad for you because the eardrum would be sucked in
and some fluid would be rushed in which would cause a severe earache.
So why would doctors suggest chewing gum if it will be bad for you in the long run?

Re: why does chewing gum help equate pressure on the ear during a plane flight?