HORMONAL changes in women over successive pregnancies could partly explain
why firstborns are more likely to develop allergies than their younger brothers
and sisters.
Wilfried Karmaus of Michigan State University in East Lansing and his
colleagues have found that firstborn babies have higher levels of a key immune
protein associated with allergies.
Epidemiologist David Strachan, now at St George’s Hospital Medical School in
London, was the first to notice that the bigger a family is, the less likely its
youngest members are to have allergies such as asthma, hay fever and eczema.
Other studies have confirmed this. “I don’t think…
