Can cockroaches help prevent asthma?

Young children living in households with pests like mice and cockroaches along with pet cats might have a lower risk of developing asthma by age 7, a new study shows.

The research published last month in the journal of Allergy and Clinical Immunology contradicts some previous findings that cockroach allergens cause asthma.

Pittsburgh pediatrician and asthma researcher Deborah Gentile said she's taking the study seriously.

“I'm not discounting this at all,” said Gentile, who works at of Pediatric Alliance health care system in Allegheny County. “There are some hypotheses about building up certain immunities through exposure to bacteria.”

Researchers examined 442 inner-city children living in St. Louis, Baltimore, Boston and New York City. They analyzed dust and found that those around higher levels of allergens as an infant were less likely to develop childhood asthma, a lung disease marked by inflammation of the airways.

Cockroach allergens were shown to protect most against asthma, with mouse and cat allergens also showing a benefit.

“Our findings suggest that primary prevention strategies for childhood asthma in low-income urban communities should probably not focus on home allergen reduction and that exposure to a broad variety of proteins in early life might have health benefits with respect to asthma,” researchers wrote in the study.

Gentile said the findings support a concept “hygiene hypothesis.” She said lack of exposure to allergens and bacteria in early childhood may hinder strengthening of the immune system, causing problems when it is later exposed.

Anecdotally, Gentile said she's treated patients who grow up in a home with cats and never exhibit allergy symptoms.

“They they go away for college, come home at Thanksgiving and all of the sudden they're allergic,” she said, explaining that their resistance may have depleted during time away from home.

By analyzing the childrens' umbilical cord blood, researchers also found that those who had been exposed to tobacco smoke in utero had a higher risk of asthma. Higher asthma rates were also connected to mothers reporting high levels of stress and depression.

Of the 442 children, 29 percent (130) had an asthma diagnosis by age 7. Higher amounts of cockroach, mouse, and cat allergens measured in house dust during a child's first three years of life were linked to a lower risk of developing asthma.

Gentile said the research could ultimately show that cockroach allergens possibly contain protective bacteria against asthma.

“There's still no clear-cut consensus with allergies, but we know that when babies first come home from hospital, they don't have allergies or asthma yet,” she said.

The study was federally funded and included researchers at Washington University, Boston University, Columbia University, Johns Hopkins University, U.C. San Francisco and the University of Wisconsin-Madison.

Ben Schmitt is a Tribune-Review staff writer. Reach him at 412-320-7991, bschmitt@tribweb.com or via Twitter at @Bencschmitt.