Children in families with cats or dogs have fewer pet allergies than new pet owners or those who had only exposed earlier in life.  A 2005 study by researchers at the Central Hospital of Norrbotten (Sweden), which tracked 2,454 children for four years, found that, in all cases where allergies were not a result of genetics, exposure to animal allergens protected boys and girls from developing allergies.  A previous study, conducted by researchers at the Institute for Social Pediatrics and Adolescent Medicine (Germany) found that children who were continually exposed to pets (in this study, cats) were 67% less likely than other kids to develop asthma and 45% less likely to develop hayfever. 

"A faithful friend is the medicine of life." ~ Apocrypha