Hi, occasional smoking is equally harmful if not more than regular smoking. The red area can be because of irritation of the mucosal lining of the throat by smoke and it is a common finding in smokers. If your doctor told you that it will definitely turn to cancer,, the he/she must have thought it to be suspicious. This is an all the more reason to quit smoking. Also, I would like to tell that stopping smoking completely and suddenly is the only method of cessation and all the methods where a person tries to stop smoking by gradually decreasing it are a failure. Please seek the help of a counsellor if you need for cessation but it is always advisable to stop tobacco use. Regards