How do I get my child to stop coughing at night from his asthma?

Controller meds. Nighttime coughing is a common symptom of uncontrolled asthma. If your child has house dust mite allergy encase pillow, mattress & comforter in miteproof covers. If pet allergic banish the animal from the house. Consider a hepa filter for allergy control but avoid humidifiers. The latter increases mold and dust mite. Use inhaled corticosteroids or singulair (montelukast) daily to control airway inflammation.
See doc. See your doc. The child probably needs an inhaled corticosteroid medication such as pulmicort, qvar, Flovent etc. Frequent night cough is a sign of uncontrolled asthma. The inhaled corticosteroid medications reduce inflammation and swelling in the airway. He or she may need some other medication as well such as zyrtec or claritin (loratadine). Also dust mite precautions such as a zippered mattress cover helps.
Better control. The whole premise to asthma is prevention. If having problems he needs a rescue drug and you need to use it often to improve the symptoms. But if the preventive medicine is the correct dose your child should have little to no problems, night or day, talk with your doctor tyou may be not giving the correct medicine.
Possible allergies. If your child's asthma is well controlled with an inhaled steroid and rescue inhaler, a lot of times, allergies causing postnatal drip are the main cause for restless, sleepless nights and night time coughing. You may want to add an allergy medicine and an expectorant to help control the cough.Drink plenty of fluids , too.See your doctor if condition worsened or no better.