Allergens widespread in largest study of United States homes

Published online: November 30, 2017

Indoor allergens are important risk factors for asthma and respiratory allergies. While their role in the development of allergic disease is not fully understood, increased exposure to indoor allergens can trigger and exacerbate asthma and allergy symptoms in sensitized individuals. Only a few studies have investigated residential allergen exposures on a national scale; the National Health and Nutrition Examination Survey (NHANES) 2005-2006 is the largest and most comprehensive study to date.

In a recently published research article in The Journal of Allergy and Clinical Immunology (JACI), Salo and coworkers investigated the importance of various participant and housing characteristics, including sociodemographic, regional and climatic factors, in residential allergen exposures. They estimated the exposure burden to individual and multiple allergens, and identified independent predictors for these exposures, using data collected on more than 7,000 Americans participating to NHANES 2005-2006. Concentrations of 8 common indoor allergens (cat, dog, cockroach, mouse, rat, Alternaria, and two types of dust mite allergens) were measured in dust collected from participants’ bedrooms.

The authors found that over 90% of homes had three or more detectable allergens, and 73% of homes had at least one allergen at elevated levels. The presence of pets and pests contributed strongly to increased allergen levels. Housing characteristics also mattered – elevated exposure to multiple allergens was more likely in mobile homes, older homes, rental homes, and homes in rural areas. Exposure to individual allergens showed variation with age, sex, race, ethnicity, and socioeconomic status. Differences were also found between geographic locations and climatic conditions. For example, elevated dust mite allergen levels were more common in the South and Northeast, and in regions with a humid climate. Higher levels of cat and dust mite allergens were found in rural areas compared to urban settings.

To provide a more complete picture, the researchers compared allergen exposures and previously reported sensitization patterns from this national survey. Both differences and overlaps were found. Although males and non-Hispanic blacks were less likely to be exposed to multiple allergens, sensitization was more common in these groups, compared to females and other racial groups. Patterns also differed for urban and rural settings. Exposure to several elevated allergens was most prevalent in rural areas, whereas sensitization rates were shown to be higher in urban areas. However, overlapping patterns were found for some individual allergens. Exposure and sensitization to dust mite allergens was most prevalent in the Southern and Northeastern regions of the United State, and cockroach allergen exposure and sensitization was more prevalent in the South. Patterns also reflected socioeconomic variations, especially for pet and cockroach allergens.

This report demonstrates that residential exposure to multiple allergens is common in United State homes. The findings provide beneficial information to a wide audience from patients to clinicians, identifying factors that influence levels of exposure to individual and multiple allergens. Differences and overlaps between exposure and sensitization patterns in the United States population highlight the complex nature of the relationships between allergen exposures, allergic sensitization and disease.

The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

Close-up of pine tree branches in Winter Close-up of pine tree branches in Winter