Wow I wish my child could go one day without coughing. Coughing is a very typical part of CF. My son coughs every morning for about 3-4 hours straight, more from the mucus that has built up over night. He is 15 and is old enough to describe what it feels like. He says, its starts with an urge to cough, and then pretty soon the cough causes an irritation causing him to cough more. Sure its possible it could be a "habit cough" but I am pretty sure about 80% reading these boards here will tell you that you were very lucky to go years and years without your son coughing at all. That is a good sign that he might not be plagued with recurring lung infections (usually Pseudomonas type of infections) that most CFers commonly get.
Also to the poster about how you struggle as a parent asking your child with CF to stop coughing. Don't feel guilty about it. Most parents go through this struggle. I have dealt with it for 15 years now, it use to really bother me. I felt hopeless, I felt like I wish I could take that cough away from him, I wish I could have bare the cough (which I know hurts him and his ribs and muscles) and take the pain and put it on me instead. I would say this to you, don't beat yourself up about it. It is a natural response, some may feel embarrassed. Some may feel shamed that you even feel embarrassed. Just know that its the hand you were dealt and also the hand your child was dealt. Does it suck? Yes, the hell it does. Do you have a right to feel mad? Yes, you do. But put that anger and fight it down and put it to more of a positive use.
To the original poster, how are your son's lung functions (PFT)? Are they above 70%, 80%? This is great news. To give you some hope here. My son coughs daily, its a usual thing in my house. Every morning this is his thing, its a struggle to get a 15 year old to do his treatments, its a fight every day. Of course he loses in the end lol <img src="i/expressions/face-icon-small-smile.gif" border="0"> The parents always win! But on a serious note, try not to let it bother you so much. Yes it could be post nasal drainage that is irritating his airway. Yes it could be bronchial irritation from the weather. Yes it could be allergy induced asthma. Its important to not let your son feel guilty about it.
PS: Make sure the nurse at school is aware of his condition. My son is in the 10th grade now and our school nurse is completely oblivious when it comes to CF, sure she read about it, and claims that she has 1 other person in the school (which she pulled my son in her room and told him her name and told him to stay away from her) completely against HIPPA guidelines and yes I got pissed, but also I can see both sides why she told him. Hate how schools try to alienate those with CF, like its some sort of catch able disease (not talking about 2 CFers passing pseudomonas) but someone actually catching CF. The teachers baffle me too, they write us Emails saying "I am worried about your son's cough as it disturbs the rest of the class". You too might get these kinds of emails. I say, tell the teacher I am so sorry that my son's disease is disrupting your class but my son has every right to an education as anyone else - DEAL WITH IT, same as we have for 15 years. Sorry, just venting.
Hang in there, it does or can get better, my son blew a 104% on his PFTs the other week!!! YAY!!! So try not to let the coughs bother you so much is all I am saying and I said a lot. Just another CF parent venting. Thank you for the opportunity to vent, didn't mean to take over your thread.