Allergen and bacteria-rich living environments could be healthy for children one year and younger in inner-city areas as research indicates it may help boost immunity and thwart allergies and asthma risks later in life.

High exposure to both bacteria and allergens may help infants avoid wheeze and allergic sensitization which are precursors to allergies and asthmas, reveals a new report that studied children in Baltimore, Boston, New York and St. Louis.

"As prevalence and severity of asthma is high in inner cities in the USA, it is especially important to identify risk factors that contribute to the development of allergic sensitization and wheezing in this environment," states a report conducted by researchers at Johns Hopkins Children's Center in Baltimore, Maryland. Children in those environments for long periods do have a higher overall allergy and asthma rate, but exposure before the first birthday appears to stem the health issues later in life.

The report identified bacteria and allergens such as mouse, cockroach or cat dander. Researchers said infants exposed to all three allergen, plus high levels of bacteria benefited the most.

"We do feel that these results, especially those related to certain microbial exposures, do support the hygiene hypothesis. This is important since it has been said that the high rates of asthma and allergy in children living in inner-cities presented an exception to the hygiene hypothesis," said study author Dr. Robert Wood, chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center.

The study involved 467 inner-city newborns and tracked health over three years with visits to infants' home to measure levels of allergens. The infants were tested with blood and skin-prick tests, physical exams and parents completed surveys. The research team also collected bacteria of dust from 104 infant homes for analysis.

The study was funded by National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health, was published by The American Academy of Allergy, Asthma & Immunology and will appear in The Journal of Allergy and Clinical Immunology. It was published in the journal Allergy and Clinical Immunology.

The Centers for Disease Control and Prevention reports 7 million U.S. children are affected by asthma. A condition costing the US $56 billion each year, asthma caused 3,388 deaths in 2009.