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Breathing in other people's smoke may cause asthma in children.¹ And smoke can also trigger an asthma attack (when symptoms suddenly get worse).

Tobacco smoke contains many different chemicals. Some of these chemicals can make the tubes in your child's lungs swollen or narrower. Some children get asthma symptoms when they go into a smoky room.

Air pollution probably doesn't cause asthma. But it can make symptoms worse. These are some of the chemicals that can cause asthma symptoms:

• Nitrogen dioxide (NO2)
• Ozone
• Sulfur dioxide (SO2).

If there are warnings that air pollution is bad in your area, you might want your child to stay inside.

Some children get an asthma attack when they breathe in cold air.² This might happen when your child goes outside.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.