chronic cough driving me up the walls

[BirthdayBabe]

dd1 is 3.6yo and has been coughing for over a year. It comes and goes, we can't find an obvious cause but it is really annoying these days so I've decided to take her to the doc. He's tested for allergies, came back negative. He's now testing for reflux but I'm very dubious.
What else could it be ? any experience ? it's a dry cough with a lot of throat clearing too. She only coughs during the day.

Sometimes the allergy tests at the doctors are not very comprehensive, it could be something as simple as an allergy to the soap powder or to dust, maybee her body is not making enough mucus, which could be why the cough's dry?? Have a look to see if there is a pattern (washing powder/ temperature/ weather), is it better on some days then others? I think she needs a referral to ENT at the hospital.