Is it ok to use plain saline in a nebulizer to help my 4 year-old with nighttime coughing. she doesn't have coughs during day only when lying down. ?

Yes..ok to use: Basically the same as using saline drops into the nose, only it is in vapor form. You can also just put some clean tap water..An alternative is get an ultrasonic humidifier which can run for many hours instead of just few minutes with nebulizer. If coughing is persistent, have her evaluated for possible nocturnal asthma etc... Good luck.

No...: Plain saline nebuluzer can actually induce bronchospasm and cough. She should be seen by her doctor for evaluation and treatment.

Yes but: You may want to work with her doc on the problem.This is often triggers by postnasal drainage from environmental irritants. Fragrances/dust/spoke/cleaning odors can all make a kid drain and cough. If the cough is due to irritants, the nebulizer helps wash them out, but avoiding them could end the problem.