I don't know anything about lobelia (I remember hearing about it recently, though, so maybe that person will come forward)...but I DO know that what gets rid of a dry cough...and starts the healing process. (gets you started on coughing up 'stuff') is...a Pear Fast.
The 4 Day Pear Fast is a great detoxifier and will also clear up and heal your lungs/cough. It rreeeaallly will! I've seen it! So...this could be just what your body wants. Drink lots of warm water, while eating only pears when you're hungry. (6 to 10 a day?) Organic only.
Then you could move right into the Master Cleanse....when you're done that.