Has your friend been to the doctor yet?
The majority of dry chronic coughs are attributed to: Post Nasal Drip, Allergies, Asthma and Acid Reflux.
Acid reflux can be present without any other symptoms so don't rule it out just because you friend doesn't have heartburn.
Another cause of chronic dry coughs is Pertussis. Incidents of Pertussis are on the rise in this country. Pertussis is nicknamed the 100 day cough. If you suspect this, your friend really should see a doctor.
I have all of the above with a chronic cough as my primary symptom for most when they flare. With the symptoms you described, I'd really read up on Pertussis. When I had it, it lasted about 4 months. I would cough so hard that I had trouble catching a good breath in between coughing. I also coughed so much that I would vomit. I also got really bad muscle pulls in my stomach and sore ribs as a result. Pertussis can be very contagious to treatment is a must. The cough has to run its course though. The best my doc did was to give me something to help me sleep at night because my body got so worn out.
