According to the National Institutes of Health, 15.7 million people in the United States have asthma. Furthermore, almost one in every ten children is affected by asthma. In addition to routine doctor visits for asthma follow-ups, almost 2 million asthma sufferers require emergency treatment each year. From around 1980 until the late 1990's, the U.S. saw a dramatic increase in the number of new asthma cases. The exact explanation for this is not clear, but a number of theories have been suggested.  

1. Increased exposure to allergens

Not only has asthma become more common in the U.S., but allergies have also. Part of the reason for this is of our own making. Wall-to-wall carpeting in our houses provides fertile ground for dust mites to thrive. By staying indoors, we have more exposure to house mites, molds and animal dander. By cutting down forests, we allow ragweed and other allergenic grasses take over.


2. Pollution

Pollution may not cause asthma, but it does appear to make symptoms worse. The Environmental Protection Agency monitors air quality throughout the U.S. and reports the AQI (air quality index) on a daily basis. Five major air pollutants---ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide are considered in formulating the AQI. The lower the AQI, the better, with acceptable readings being up to 100. When the AQI is over 100, it is recommended that asthmatics limit their physical activity. At even higher levels, they are advised to remain indoors.

3. Cigarette Smoking

For obvious reasons, smoking is harmful to the respiratory system. Cigarette smoking represents an important "trigger" for the development of allergy symptoms. It has been found that children who live with smoker are much more likely to develop asthma than those in non-smoking households. This may be because their lungs are smaller and have yet to fully develop. With the prevalence of smoking somewhat on the decline, it will be interesting to see if the incidence of asthma drops off proportionately.

4. "Over-sanitization"

This is one of the most interesting theories to explain the increasing prevalence of asthma. Prior to the age of widespread use of antibacterial products in the household, children were exposed to, and eventually developed immunity to a variety of bacteria and "germs". It is thought that this immunity provided some protection against the development of allergies and asthma. Likewise, even though pet allergens are known to be a potent trigger of asthma, there is recent evidence that infants are less likely to develop allergies or asthma if cats or dogs are present in the house during the infants first year of life.

Recognize that all of these are theories and there is much work to be done to determine the exact reason that asthma is on the increase. A common thread among these causes appears to be our increasingly home-bound lives. Spending more time outside, breathing fresh air and striving to live a "clean" but not necessarily sterile life may be one of the keys to reversing this trend.