填空题 Some scientists think that parents make too big fuss about hygiene, and that daily 1
contact with bacteria and viruses can be good for youngster. A recent study conducted 2
by the University Children"s Hospital in Munich showed that children who had
at least two mild virus infections before their first birthday were only the half as 3
likely to be diagnosed with asthma or allergies when they were seven, compare with 4
children who had been ill only once or not at all. This finding supports the hypothesis 5
that today"s nltra-clean lifestyle is the reason of an increase in allergies in the general 6
population in developed countries. It is possible, although this is not yet establish, 7
which contact with the bacteria is needed for cells in human immune systems to 8
develop correct. So parents should not overreact if their children get muddy or 9
dirt sometimes when playing outside. 10