I had a cold and a chest infaction a few weeks ago. I toked up as much as possible and in 2 days my cold and comlpetely gone and so had my chest infection, and i didnt even need anti-biotics.

As for asthma it does help, and will NOT give you bronchitis. It helps asthma sufferers because the THC dialates the bronchi.

Smoke and see if it helps, if it gets worse then stop. As for the sore throat it might help ease the pain.

As far as im concerned, cannabis helps every illness, and get you stoned at the same time.