Children who are exposed to more allergens and bacteria in their homes during the first year of life may be less likely to suffer from allergies, wheezing and asthma later on.
Researchers found that 3-year-olds who were exposed to mouse dander, cat dander and cockroach droppings before they turned 1 were three times less likely to suffer from wheezing, allergies and asthma than those who lived in homes without these allergens.
The 3-year-olds in the study who were free of wheezing and allergies lived in homes with the highest degrees of allergens, and were also the most likely to live in homes with the greatest variety of bacteria species.
In a recent study, a combined exposure — to both high levels of allergen, and a high diversity of microbes — was associated with a lower prevalence of allergies and wheezing.
In the study, researchers followed 467 inner-city infants in Baltimore, Boston, New York and St. Louis from birth until they were 3. The investigators visited the children's homes, collected and analyzed dust samples in 104 of the homes, and examined the level and type of allergens in the infants' surroundings.
The researchers also tested the babies for allergies and wheezing using blood and skin-prick tests, physical exams and parental surveys.
About 41 percent of the kids who were both wheeze- and allergy-free lived in homes that were teeming with allergens and bacteria. On the other hand, just 8 percent of the kids who had both allergies and wheezing problems had been in regular contact with various allergens and bacteria, according to the study.
The study authors also found that the children in the study who were exposed to all three types of allergens — from cats, cockroaches and mice — had a lower risk of allergies, wheezing and asthma at age 3 compared with those who were exposed to only one or two of these allergens.
Exactly why early exposure to dirt and bacteria may be beneficial to kids is unclear, the researchers said.
The mechanism is unknown at this time, but it is thought that these high levels of exposure result in a better educated immune system, as it develops during early infancy.
Previously, the proponents of the so-called "hygiene hypothesis" have suggested that kids these days are in fact not exposed to enough dirt and bacteria, which leaves their immune systems ready to overact to substances that should be harmless to them.
The new study shows for the first time, that the bacterial content of house dust in inner-city households is significantly associated with allergic disease outcomes of children raised in those houses.
In keeping with the hygiene hypothesis, our study shows that there may well be bacterial exposures in inner-city households that protect children raised in those environments.
Some other studies have suggested that an extraordinarily clean environment increases the risk for allergic disorders. For a couple that wants to have children, it is a very good idea to have a couple of cats or dogs.
Restricting a mother's diet of specific allergens during pregnancy and while breast-feeding, when a child is otherwise well, is not routinely recommended as a means to prevent food allergies. Most recent information indicates there is no significant allergy prevention benefit to your baby if you avoid highly allergenic foods during this time. Breast milk is the ideal way to nourish your infant. It is least likely to trigger an allergic reaction, it is easy to digest and it strengthens the infant’s immune system. Especially recommended for the first four to six months, it may possibly reduce early eczema, wheezing and cow’s milk allergy. For infants at risk for food allergy where the mother is unable to breast feed, hydrolyzed infant formulas are recommended as hypoallergenic substitutes over cow’s milk and soy formulas.
Between four to six months, single-ingredient infant foods may be introduced, typically including fruits (apples, pears and bananas), vegetables (green vegetables, sweet potatoes, squash and carrots) and cereal grains (rice or oat cereal) one at a time. Food can be introduced this way every 3 to 5 days as appropriate for the infant’s developmental readiness. This slow process gives parents or caregivers a chance to identify and eliminate any food that causes an allergic reaction.
Egg, dairy, peanut, tree nuts, fish and shellfish can be gradually introduced during the same four to six month window after less allergenic foods have been tolerated. In fact, delaying the introduction of these foods may increase your baby’s risk of developing allergies.
When allergies are suspected to develop because allergies run in the family it is even more important to expose them early enough to allergens and by all means, to do this with the help of an allergist.