Doctors are uncertain about what to blame for the climbing number of asthma cases.
But why there's more of it, and why it's worse than ever, is the big question. Heat, humidity and pollen also add up to miserable days for people prone to allergies and asthma. While many are quick to blame smog and the urban ozone created by too many cars, air pollution is just one of the culprits, experts say. Other factors have converged with smog to bring about the asthma epidemic, such as home design, a sedentary lifestyle and a diet loaded with fat and preservatives. People stay inside homes breathing in allergens their grandparents did not.