Nonstop Coughing

Our nearly 3 year old has had a cough on and off for months. He refuses medicine, saline spray, inhaler, etc. He’s starting to cough through the night and it’s impacting his sleep but he won’t let us help him. Any ideas on what will soothe his cough? We have a humidifier…or any tips on how to get him to take meds?! He’s so strong willed…