S/O coughs

Last night and this morning I have heard DS cough while in his crib only a couple times in a row and he doesn't do it while awake.  What would I attribute this too?

I just assumed it was just a random cough when it has happened before but now I am wondering.  Before it would only be one or two coughs and it never happened two days in a row.

It doesn't help that I found out yesterday that DH didn't quit smoking while he was on deployment like he had led me to believe.  I found this out because he went to the store to get some stuff for us and awhile after he came back I smelled it on his hand.  I got really irritated with him because I had told him before that if he was going to continue smoking he had to change his clothes and wash up before holding DS and he didn't.  And I noticed while I was feeding DS after DH had come back that there was this rash on his face and neck and I couldn't figure out where it would have come from because nothing had changed.  After I put DS down for his nap I was thinking about it and after DH had come home from the store he got DS up from his nap and changed him and brought him to me so I could feed him.  So now I think the rash has something to do with the fact that DH smoked and then didn't clean up before holding him and now I am wondering if the cough is because of that too.