How many people in the U.S. are allergic -- to ragweed pollen, cat dander, or food? What sort of impact do allergies have on society? Here's a rundown of some of the most important allergy statistics -- based on the best available data.
Number of people in the U.S. who have either allergy or asthma symptoms: one in five.
Percentage of the U.S. population that tests positive to one or more allergens: 55%.
Rank of allergies among other leading chronic diseases in the U.S.: 5th.
One estimate of the annual cost of allergies to the health care system and businesses in the U.S.: $7.9 billion.
Number of workdays lost each year as a result of hay fever: 4 million.
Number of weeks by which the ragweed pollen season has increased in the last 10 to 15 years, likely as a result of global warming: four.
Odds that a child with one allergic parent will develop allergies: 33%.
Odds that a child with two allergic parents will develop allergies: 70%.
Number of ER visits in the U.S. caused by food allergies each year: 30,000.
Percentage of the people in the U.S. who believe they have a food allergy: up to 15%.
Percentage of the people in the U.S. who actually have a food allergy: 3% to 4%.
Percentage of our lives that we spend indoors: 90%.
Degree by which levels of indoor pollution in U.S. homes exceed levels of outdoor pollution: two to 100 times, depending on factors such as whether the residents smoke.
Percentage of U.S. households with one or more dogs: 39%.
Percentage of U.S. households with one or more cats: 33%.
Percentage of all U.S. households with detectable levels of dog and cat dander: 100%.
Percentage of people in the U.S. that have asthma: 8%.
From 2001 through 2009, asthma rates rose the most among black children, almost a 50% increase.
On average, in 2008 children missed 4 days of school and adults missed 5 days of work because of asthma.
Percentage of people hospitalized for asthma who are children: About 44%.
Number of deaths each year in the U.S. from asthma: 3,447 in 2007.
Number of people with chronic allergy-like symptoms -- runny nose, congestion and cough -- but who have nonallergic rhinitis instead: one out of three.
SOURCES: American Academy of Asthma, Allergy, and Immunology web site: "Patient/Public Education: Fast Facts, Allergies," "Tips to Remember: Rhinitis," "Allergy Statistics," "Asthma Statistics." American Lung Association: "Home Environment: A Guide for Creating a Healthier Home." Asthma and Allergy Foundation web site: "Allergy Facts and Figures." The Humane Society of the United States: "U.S. Pet Ownership Statistics." Jay M. Portnoy, MD, president of the American College of Allergy, Asthma and Immunology (ACAAI); chief, section of allergy, asthma and immunology, Children's Mercy Hospitals & Clinics in Kansas City, Mo.