It has generally been thought that keeping a house clean with air filters, non-allergenic bedding, and other measures to keep dust and dirt away from children would help to prevent allergies. During the past decade, however, researchers have found that exposure to dust and dirt during early childhood, especially in the first year of life, may actually be protective. Such exposure is thought to activate aspects of immunity that keep allergy and asthma at bay.
In a study from researchers at the Institute of Social and Preventive Medicine in Basel, Switzerland, 812 children living in rural parts of Austria, Germany, and Switzerland were evaluated. The researchers compared children who lived on farms where they are constatnly exposed to animal dander and bacteria from animal waste to children who did not live on farms. Samples of dust from children's mattresses were analyzed for endotoxin (substances known to cause allergic irritation in sensitive people) content, and blood samples were analyzed for markers of allergic inflammation. Far more endotoxins were found in the farm children's bedding, but higher endotoxin levels correlated with deceased blood markers of allergic inflammation. The likelihood of asthma, hay fever, and atopy (allergic skin irritations) was approximately 50 percent lower in farm children, and their immune systems did not respond dramatically to those endotoxins. In other words, their immune systems were better at discerning what was actually a threat.
Children don't need a spic-and-span environment, and their attraction to dirt and grime may be Mother Nature finding a way to expose them to endotoxins that help their immune systems to develop properly. This is yet another reason why it's so terrific for children to grow up around animals. Your dogs or cats don't only protect your child against boredom and loneliness, they also protect them against allergies!