My 3yrs old daughter coughing 1 month just when sleeping in morning. good at stethoscope. pneumoslides negative. total ige negative. what can it be?

Many possibilities!: Crucial basics: understanding the nose & lungs mucociliary escalator: http://goo.gl/IXDw19. Cough is a backup mechanism when the built in system is overloaded, during periods of ↑ed inhaled dryer cooler air, emotional grief (↑ed mucous secretion), etc. Possible helpful treatment strategy? The mypurmist device using ONLY distilled water: humidify&warm inhaled air; assist the mucociliary escalator.