My post nasal drip cough has been bothering me for a month. Although I used nasal steroids and oral antihistamines, they were only partially successful. Although the throat showed no signs of infection, the ENT specialist saw a little inflammation in the back of the nose. Mucus is now arriving less, which is an improvement from earlier. I feel better after inhaling steam. Most coughing happens in the evening. What are some more causes of postnasal drip?