My middle son had pneumonia when he was four months old. This contributed to a weakened immune system his whole life. The minute he would get a little bit of a cold, it would go straight to his chest. After several years of constant trips to the doctor for bronchitis, at 4 years old I started treating the cold/cough at the first onset of symptoms. I would immediately boil water and make a "croup tent". I would let it cool down a little bit, then put it in a bowl, take a large bath towel and have them lean over the bowl with the towel over their head (holding it out like a tent), this holds in most of the steam. IT IS VERY IMPORTANT THAT YOU DO NOT LET THEIR HANDS OR FACE GET TOO CLOSE TO THE BOWL! Have them take in deep breathes of steam. You will have to give them a break after a few minutes, then repeat the steps. They will immediately start to cough as they take in the deep breathes, just have them continue doing it, it will subside. The next step is to rub warm (not hot) Vicks on their chest and back. Make sure you rub it all the way down to where their lungs are on their back. Put a t-shirt on and put them to bed.
It can be a little tricky at first, but after doing it a few times, it becomes very simple and it seems to work better than a humidifier. Make sure that you do this procedure at the very FIRST signs of a cough.
This has saved me a lot of time and money. I still do this for all of my kids and stepkids, even now that they are teenagers, they don't like it, but they know it works! I hope this information is helpful and will save you trips to the doctor also.