Once the room is all fogged up, take him in there for 10-30 minutes. Try to help your child not be afraid by cuddling or reading a story. Repeat as needed. While hot humid air relaxes the cough reflex and loosens the secretions, cold clear night air reduces airway swelling and may be used if the foggy bathroom is not completely effective. Freezer air may do if it is a warm night.
Most children settle down with the above treatments and then sleep peacefully through the night.
Mist and humidity Dry air usually makes coughs worse. Keep the child's bedroom humidified. Use a cool mist humidifier if you have one. Run it 24 hours a day. Otherwise, hang wet sheets or towels in your child's room.