Suggest Cure For Infection In The Chest & Runny Nose

My son is 11 months old, 25lbs, and has a runny nose. I think it s due to the pollen count being so hight outside. The problem is at nap and night he coughs so much he cannot sleep. We re running a humidifier, but it s not helping. We re going on night 2 of no sleep and he has even thrown up the bottle he just drank due to the coughing. My ped told me to give him an OTC cold and cough but I cannot remember the dose. My 2 year old takes 1tsp. Any suggestions?