Dust mites and pets are not the only contributors to asthma in inner-city children. Cockroaches cause more serious problems, according to a study reported in the Journal of Allergy and Clinical Immunology (March 2005). The researchers said that allergic reactions to cockroaches are the major contributors to childhood asthma in inner-city homes. The study's findings indicated that many homes tested in northeastern cities had high levels of cockroach allergens. Homes in the southern and northwestern regions of the United States had enough dust-mite allergens to aggravate asthma symptoms.