By Beth Thomas Hertz

It’s well documented that asthma and allergies are more common in children today than 100 years ago. Why? Doctors and scientists offer a host of theories: family history, poor lung development early in life due to premature birth or respiratory disease, a dramatic rise in obesity, climate change and exposure to tobacco smoke, to name a handful.

Another often-cited reason is that we live cleaner lives than our ancestors. While improvements such as safe drinking water and good sanitation have saved countless lives, some children may not get exposed to bacteria that challenge and ultimately strengthen their immune systems from an early age.

Across the United States, asthma and allergy rates are largely the same, with a few exceptions: higher in poor urban areas and lower in rural, farming regions.

While overall asthma rates in children declined to 8.3 percent in 2013, prevalence continues to rise among children in poor families and the disease remains far more common in African-American and Hispanic children, according to the U.S. Centers for Disease Control and Prevention (CDC) National Center for Health Statistics.

The challenge in urban areas

High rates of allergies and asthma in the inner city have resulted in more missed school days, more missed work days for their parents, and a greater likelihood of emergency department visits and hospitalizations, says Stephen Teach, MD, a pediatrician with Children’s National Health System in Washington, D.C., and director of IMPACT DC (Improving Pediatric Asthma Care in the District of Columbia), an interconnected program involving asthma care and research.

“The rate of emergency department visits among kids with asthma in the inner city is much higher than elsewhere,” he says.

One reason for this may be increased exposure to environmental allergens and irritants that trigger asthma symptoms, such as mold, dust mites, cockroaches and mice, cigarette smoke and diesel exhaust from living near highways.

Another reason is poverty, which can affect access to preventive medications and healthcare. Psychosocial stress is also a factor, such as when a child is exposed to violence in his or her neighborhood, Dr. Teach says. The problem is compounded when children in unsafe neighborhoods stay indoors because they do not feel safe outside or have no green spaces on which to play.

“By staying indoors, young children and infants are not exposed to a more natural environment that may lead to more ordered development of the immune system,” he says.

These children also may not get enough vitamin D from the sun, increasing their risk of developing respiratory infections and leading to a worsening of asthma symptoms. “Low vitamin D levels may play a role in making children susceptible to allergic diseases of all types, including asthma, food allergy and eczema,” he says.

Future research will focus on helping the immune systems of young children develop in a healthier way. “We might be looking at things like asthma vaccines, or exposing children to dirt and animals early in life in a way encourages a healthy development of the immune system,” Dr. Teach says.

Living in rural areas

Children growing up in rural environments may have lower prevalence of asthma and allergies in general because they have been exposed to more dirt and animals from an early age.

Mark Holbreich, MD, a board-certified allergist and researcher in Indianapolis, provides care to Amish children in his practice and has observed a low rate of asthma and allergies in that specific population.

Dr. Holbreich partnered with German allergy expert Erica Von Mutius, MD, on research comparing Amish children, Swiss children who live on a farm, and Swiss children who don’t live on a farm. Positive allergy skin tests were seen in 7 percent of Amish children, 22 percent of children on Swiss farms and 45 percent of non-farm children.

Dr. Holbreich and Dr. Von Mutius believe low rates in the Amish are due to very early childhood exposures to farm life, farm animals and the foods those animals eat. Barns are often close to homes and women work in the barn while they are pregnant, so infants with developing immune systems are exposed early on to animals.

Meantime, other researchers are analyzing dust, farm animal waste and other particles from Amish farms to determine if there are components that protect against asthma.

When families ask Dr. Holbreich if taking their child out to the country for visits, or even moving to a rural area, will help protect them against allergies and asthma, he says no. “Only certain very unique farming circumstances seem to offer protection. There is no data to suggest that having a more rural life in general is going to make a difference,” he says.

People in rural areas who develop allergic diseases face a different set of triggers than those in cities. They are likely exposed to more plant and tree pollen, mold spores and harvest dust as well as pollutants from people burning wood or coal for heat.

And air pollution is not just in cities – particles are easily transported by wind to suburbs and rural areas.

Living in rural areas can also mean they must travel farther distances to see asthma and allergy specialists, although Dr. Teach says most patients can be managed by properly trained primary care doctors. For those who need more specialized care, telemedicine — communicating with doctors online via videoconference and smartphone apps — can help.

“Much of the physical examination and history can be done remotely,” he says. “Spirometry and other lung function measurements can be done locally and then transmitted. Even skin testing or blood allergy testing can be done locally, with that information sent to a specialist remotely.”

Improving the health of your home

Whether you live in the inner city, the suburbs, an exurb or a rural area, there are things you can do at home to help reduce allergy and asthma symptoms, says Ruth Ann Norton, president and CEO of Green & Healthy Homes Initiative (GHHI).

Headquartered in Baltimore, the organization has worked to reduce allergens in housing since the mid-1990s as an outgrowth of its work to address lead hazards in homes.

“We look at homes holistically for environmental health impacts with an emphasis on asthma triggers,” she says.

GHHI conducts home interventions primarily in urban and rural communities across the country, with counselors and contractors visiting houses and apartments to evaluate indoor air quality and structural defects such as burst pipes or leaky windows and roofs.

Increasing energy efficiency is important, as it helps reduce extreme heat and cold swings that can trigger asthma, Norton says.

GHHI also works to address behavioral issues – teaching families the importance of taking all medication as prescribed and changing air filters regularly.

Families are given tools – HEPA (high efficiency particulate air) vacuum, mattress covers and nontoxic cleaning materials – to help them maintain a healthy indoor environment.

Practical tips to reduce triggers

  • Moisture leads to mold, so repair any leaky pipes and keep gutters clear.
  • Reduce leaks in windows and doors.
  • Use only nontoxic products for pest management.
  • Use dust-mite-proof mattress and pillow encasements.
  • Use a HEPA (high efficiency particulate air) vacuum that helps prevent allergens from escaping into the air.
  • Get rid of wall-to-wall carpeting if possible and use hardwood floors.
  • Take steps to manage pet allergens. Always keep animals out of the bedroom. When brushing them, do it outdoors to keep out dander.
  • Do not leave food out and keep trash cans sealed with heavy lids to reduce pests.
  • Do not use air fresheners, scented cleaning products or candles.
  • Stop smoking, or at least do not smoke in the home or car so the residue doesn’t get into walls or in fabrics. Smokers should change their clothes before being around children. The CDC offers tips and resources to help increase your chance of being smoke-free for good.
  • Use a HEPA air filter and change it regularly.
  • Make sure dryers are venting properly, as well as kitchen and bathroom fans.
  • Talk with your healthcare provider about how to prevent and avoid asthma and allergy triggers in your environment. For more information on Green & Healthy Homes Initiative, visit

Explaining the ‘Hygiene Hypothesis’

The hygiene hypothesis suggests that the cleaner a child’s early environment, the more likely he or she is to have asthma or allergies. Why? The thinking goes that as young children are exposed to millions of microorganisms and bacteria, their immune system becomes trained to better withstand allergens and irritants.

This concept was first proposed in the late 1980s by a London doctor named David Strachan who found the more children there are in a family, the lower the rates of allergy and asthma.

“The idea was that when you have a lot of children in the house, they are exposed to more colds and more dirt,” says allergist Mark Holbreich, MD. “The hygiene hypothesis has changed over the years to now suggest that as children are exposed to fewer infections, get immunizations and live in cleaner environments, they develop more allergies.”

It could also depend on the type of bacteria present in an environment. Some children may be exposed to more helpful bacteria that can build immunity to allergens, while others may be exposed to more harmful bacteria that can predispose them to asthma. Research is ongoing.


Reviewed by Bradley Chipps, MD and Eileen Censullo, RRT