We are visiting with my parents in Florida, where it's a little colder than what we are used to. I noticed that my son keeps scratching his ears and this morning there is an off smell coming from his nose/mouth area. I breath his teeth, but it still there so I figure it's coming from inside. Could it be a sinus infection?

I would check with a doctor to be sure but that does sound like something. Is he having any discharge or any other symptoms that you can tell?

I'm not sure scratching his ears is a sinus infection, although he could have started with an ear infection that settled/spread to his sinuses. I had that problem alot. because the ears/nose/throat are connected infections can and will travel around if they start in one.

In the meanwhile feed him carrots and pumpkin, cooked or raw to help with the possible ear infection. pumpkin pie made in custard dishes instead of crust is a good way to get it down. It works great and is a better alternative than anti-biotics for reoccurring issues.

is it possible he put some food up his nose and it is rotting? You'd be shocked how they can stick something up there when your back is turned and you don't know until there is an infection. Happened to my nephew.