Secondhand smoke can trigger asthma episodes and increase the severity of attacks. Secondhand smoke is also a risk factor for new cases of asthma in preschool aged children who have not already exhibited asthma symptoms. Scientists believe that secondhand smoke irritates the chronically inflamed bronchial passages of people with asthma. Secondhand smoke is linked to other health problems, including lung cancer, ear infections and other chronic respiratory illnesses, such as bronchitis and pneumonia.
Many of the health effects of secondhand smoke, including asthma, are most clearly seen in children because children are most vulnerable to its effects. Most likely, children's developing bodies make them more susceptible to secondhand smoke's effects and, due to their small size, they breathe more rapidly than adults thereby taking in more secondhand smoke. Children receiving high doses of secondhand smoke, such as those with smoking mothers, run the greatest relative risk of experiencing damaging health effects.