Children on average get 6-12 colds per year. Here in Australia there has been shown to be a strong correlation to children not getting sick in their first year of life & the higher incidence of allergy & asthma when they get older... "infantile" asthma (which my ds#1 has found in 0/1-5yo has something like an 80% chance of them growing out of it & tends to be more genetic)
While it is a pain to have a sick child, lack of exposure to "pathogens" (germs) doesn't give the immune system a chance to be stimulated & can make it more likely to react "to self" with autoimmune diseases.