chronic dry cough

My 10 year old granddaughter has a chronic dry cough. I mean every minute she coughs all day
long. She has been to the allergist and has been tested for allergies. The allergist confirmed
her allergies, and said the cough is from post nasal drip.
I was able to personally experience her sleeping thru the night and she was NOT coughing while
she sleeps. My kids believe she isnt coughing because of the nasal spray for the post nasal.
I am very concerned about this cough. Its has been months now and it has not gone away
with her spray. It is even more concerning because she has mentioned the kids in school make fun
of her. Please help.  

[National Jewish Health]

There are many causes of cough including asthma, postnasal drip, and gastroesophageal reflux disease (GERD).  GERD is the back flow of stomach contents, including digestive juices, into the esophagus or food tube and sometimes as far up as the throat and mouth.  There is another type, called habit cough that is just what the name suggests, a cough that might have initially had an organic cause and then became a habit.

You might want to contact the nearest children's hospital and ask if they have, either a cough clinic, or a pediatric lung specialist with an interest in cough.

The human cough reflex is significantly diminished during sleep and this may account for her not coughing while she sleeps.