Seasonal allergies can trigger itchy and watery eyes, coughing, sneezing, runny nose and a sore throat. But regularly exposing babies to bacteria and certain allergens before age one may actually be crucial to keep our immune system working well and defending against irritating allergies later in life, according to a new study published in the Journal of Allergy and Clinical Immunology.

The timing of initial exposure to allergens may be crucial, especially since wheezing illnesses affect up to 50 percent of children by age three, and are the leading cause for outpatient visits and hospitalizations. Therefore, it is important to identify risk factors that contribute to the development of allergic sensitization and wheezing to develop new allergy treatments. Dr. Robert Wood, chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center, and his colleagues, suggest modern society’s obsession with cleanliness has prevent us from coming in contact with crucial bugs that help keep our immune systems working well, increasing the prevalence of allergies.

To investigate the common environmental factors associated with reoccurring wheezing in inner-city environments, scientists at the Johns Hopkins Children’s Center and other institutions examined data from the Urban Environment and Childhood Asthma study. The birth cohort examined over 450 infants who were at high risk for asthma in Baltimore, Boston, New York, and St. Louis over a period of three years.

All of the participants involved in the study lived in an area where more than 20 percent residents were below the poverty level, had a mother or father with allergic rhinitis, eczema, and/or asthma, and were born at 34 weeks gestation or later. Clinic visits occurred at 12, 24, 33, and 36 months, and homes were visited annually beginning at age 3 months for an environmental survey and house dust collection. Allergen-specific IgE levels were measured annually for milk, egg, peanut, and German cockroach, while at two and three years of age, specific IgE levels for dust mites, dog, cat, mouse, and Alternaria species were also measured.

The findings revealed infants who grew up in homes with mouse and cat dander and cockroach droppings in the first year of life had lower rates of wheezing at age 3 compared with children not exposed to these allergens soon after birth. The researchers found the protective effect was additive, meaning the infants exposed to all three allergens had a lower risk than those exposed to one, two, or none of the allergens. Wheezing was found to be three times as common among 51 percent of children who grew up without exposure to allergens, compared with 17 percent of children who spent their first year of life in houses where all three allergens were present.

The researchers were surprised to find infants who encounter substances such as dirt, dander, and germs before their first birthdays, seem to benefit rather than suffer from allergy and asthma. “What this tells us is that not only are many of our immune responses shaped in the first year of life, but also that certain bacteria and allergens play an important role in stimulating and training the immune system to behave a certain way,” said Wood, in the press release.

These findings could also help explain why adults who may have never suffered from allergies during childhood, begin to develop symptoms in adulthood.

“There are many things that can contribute to allergies, and it depends on the compounding effect IgE how many and how much you've been exposed to and therefore how much (toxicity) your body can take,” said Birgitta Lauren, pre and postnatal fitness and nutrition in Los Angeles, Calif., to Medical Daily in an e-mail. Lauren also suggests a mother’s lifestyle habits can also influence an offspring susceptibility to allergies. “[S]moking and toxic exposure by your parents, especially during pregnancy will increase risk, malnutrition during pregnancy, medications and especially vaccines during pregnancy causes allergies, and continued vaccines during life is why older children or adults will all of a sudden start to suffer from allergies if they didn't already.”

Although the American Academy of Allergy, Asthma & Immunology, says reducing contact with airborne substances that trigger allergy or asthma symptoms may delay or prevent the onset of these symptoms, researchers have begun to find otherwise. This is supported by the rise in asthma, hay fever, and food intolerances. Increasing our exposure to bacteria, but not abandoning hygiene when it comes to the common cold or the flu, can help retune our immune systems and prevent the onset of allergies.


Wood RA et al. Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children. Journal of Allergy and Clinical Immunology. 2014.