For most kids, breathing is simple: They breathe in through their noses or mouths and the air goes into the windpipe. From there, it travels through the airways and into the lungs. But for kids with asthma, breathing can be a lot more difficult because their airways are very sensitive.

An asthma flare-up, which some people call an asthma attack or episode, happens when a person's airways get swollen and narrower and it becomes a lot harder for air to get in and out of the lungs. Sometimes the swollen airways produce extra mucus, which makes things pretty sticky, so it's easy to see why it's hard to breathe.

In between flare-ups, a kid's breathing can be totally normal or seem that way. But during a flare-up, it can feel like the person is breathing through a straw.