Wednesday , June 25, 2014 - 12:00 AM
It may be OK after all to let your baby snuggle up to the cat and roll around in the dirt.
A new study shows infants exposed to pet and rodent dander, household bacteria and roach allergens during the first year of life appear less likely to suffer from allergies, wheezing and asthma.
The study, conducted at John Hopkins Children's Center and other institutions and published in the June 6 edition of the Journal of Allergy and Clinical Immunology, showed exposure to certain allergens before a child's first birthday may have a protective effect by shaping their immune responses against allergies and wheezing, both precursors to asthma.
"Our study shows that the timing of initial exposure may be critical," said study author, Dr. Robert Wood, chief of the Division of Allergy and Immunology at John Hopkins Children's Center. "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."
Dr. Doug Jones, an allergist at Rocky Mountain Allergy in Layton, and Dr. Joseph Anderson, owner of Intermountain Allergy and Asthma of Ogden, said the incidence of allergy and asthma are increasing but the reasons are not clear. The Hygiene Hypothesis, which is what the study was based on, is a leading theory.
"The Hygiene Hypothesis is a concept that has been debated for years," Jones said. "It states that by keeping ourselves or our children 'too clean,' the normal development of our protective immune system may be hindered and people are more susceptible to becoming allergic. The early exposure to a naive immune system aids in a more normal development of our protective immunity and in developing tolerance to triggers instead of sensitivity to them."
Anderson said as an infant, the immune system is developing rapidly. There are two main types of immunity: humeral (antibody) and cellular (immune blood, tissue and bone marrow cells).
"It is the theory that because we are cleaning up our environment and preventing many childhood diseases that the immune system is going down the allergic antibody (IgE) direction," Anderson said. "Examples include lower incidence of allergy in rural areas where people are exposed to bacteria from farm animals, lower in the youngest child exposed to siblings infection, higher allergy in the developed world."
For the study, researchers tracked 467 inner city newborns for over three years, measuring the levels and types of allergens they were exposed to. 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 to children not exposed to these allergens after birth. In addition, infants in homes with a greater variety of bacteria were less likely to develop environmental allergies and wheezing at age 3.
Asthma affects approximately 7 million children in the United States, making it one of the most common pediatric illnesses, according to the U.S. Centers for Disease Control. By the age of 3, up to half of all children develop wheezing, which in many cases evolves into full blown asthma.
"I think the best thing people can do is not stress so much and just live," Jones said. "If you want a pet then get one. There is solid evidence that it may indeed help."
But people do not need to go out of their way to get a pet if they don't want one, Jones said. You can do everything correct and still develop allergies. If you do develop an allergy to your pet, however, Jones and Anderson said you don't need to get rid of the animal. Instead, get rid of the allergy.
"There are so many other factors besides early exposure to pets and germs that may lead to allergies," Jones said. "People should remember that this is one component of many."
Other factors that may play a role are genetics, pesticides, pollution, longer pollen seasons, genetically modified foods and stress.
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