Millions of Americans suffer from asthma but many don't know they have it.
On May 1, the American College Of Allergy, Asthma And Immunology begins free nationwide screenings. And on The Early Show, Dr. Emily Senay has advice on who should get tested.
This is the sixth year the free screenings have been held. About 50,000 people have been tested. In addition to the screenings, people who've already been diagnosed with asthma can talk with a specialist about ways to keep their conditions under control.
An estimated 17 million Americans have asthma. That's a 60 percent rise since 1979.