What causes wheezing?

Wheezing can be a normal healthy response to an unhealthy environment. Or, wheezing can be a sign of asthma. I'm Dr. Alan Greene and I want to talk with you for a moment about how to tell the difference, what causes wheezing anyway, and when is it healthy and when is it not. Well to understand that, first let's all take a deep breath together (inhales). When you breathe in, the air comes through your nose or mouth, through the big windpipe and breaks into 2 big bronchi, one into each lung. And from there they break into a whole bunch of little, smaller bronchioles. It's almost like a tree's branches branching out. And those bronchioles are where the wheezing happens. Let's look at a bronchiole. Here's one of those small airways. Now if you happen to walk into a cloud of something that's toxic, your body is going to respond instantly to try to protect you. The first thing that will happen is the muscles around the bronchioles will tighten, will constrict down almost like a boa constrictor, and you get the tight airways. If that toxic cloud is still there, to protect your delicate tissues deep in your lungs, swelling of the lining will happen. Inflammatory stuff to help protect you from those toxins. And if it's still there, still irritating, mucus will begin to be secreted to be able again to capture and protect you from those toxins. That's wheezing. Asthma happens when your airways are hyper-responsive. When they're twitchy. When they're hyper-alert and they respond to something that's not truly dangerous. The problem with that is when your bronchioles are constricted and swollen and has mucus in them, that narrow little opening is hard to breathe through. You have to work to breathe, especially to breath out. And that hard breathing through a narrow passageway is what creates the sound we know as wheezing.