Asthma is a chronic (long-term) disease that makes it hard to breathe. At its worst, asthma can be fatal.

For example, in 2003, asthma killed 287 Canadians 1.

Asthma can't be cured, but it can be managed. With proper treatment, people with asthma can lead normal, active lives.

If you have asthma, your airways (breathing passages) are extra sensitive. When you are around certain things, your extra-sensitive airways can:

Become red and swollen - your airways get inflamed inside. They fill up with mucus. The swelling and mucus make your airways narrower, so it's harder for the air to pass through.

Become "twitchy" and go into spasm - the muscles around your airways squeeze together and tighten. This makes your airways narrower, leaving less room for the air to pass through.

The more red and swollen your airways are, the more twitchy they become.