Egg allergy is one of the most
prevalent food allergies in children. This allergy may go away as the children
grow older, but there are greater chances that these children will develop
chronic allergies such as asthma or allergic rhinitis later in life.
Researchers believe that understanding the risk factors for egg allergy may
help understand the development of these chronic allergies later in life.
To determine the risk factors,
Jennifer Koplin from the Murdoch Childrens Research Institute, Australia, and
her colleagues investigated the role of environmental and demographic factors
on the development of egg allergy in 5196 one-year-old infants.
The major findings were -
• 10.8 percent
of infants who had no siblings were allergic to egg. Risk of egg allergy
decreased as the number of siblings increased (3.7 percent in infants with
three or more siblings). The researchers hypothesized that 'an increase in
maternal exposure to microbial stimulation during pregnancy resulting from
contact with young children is responsible for the observed decrease in egg
allergy in offspring'.
• The risk for
egg allergy was less in infants who had siblings under the age of 6 years as
compared to those who had 6-year-old and older siblings.
• 5.9 percent
of infants who had dogs at home were at the risk of egg allergy as compared
with 10.2 percent of infants who did not have dogs at home, suggesting that
microbial exposures associated with pet keeping could be the reason for
decrease in allergy risk.
• There was no
association between caesarean section delivery and subsequent egg allergy. Even
the children of allergic mothers delivered by caesarean section were not at
increased risk of egg allergy.
infants were less likely to be egg allergic. The researchers suggested that
this may be due to 'differences in the type and timing of trans-placental exposure
to allergens, pathogens or gastrointestinal flora'.
use of antibiotic in infancy, childcare attendance and the age of the mother
were also not associated with egg allergy.
• Having one or
more parents born in East Asia was a high risk factor for egg allergy.
'Interestingly, parents born in East Asia were less likely to report a history
of allergic disease themselves, while their infants are at increased risk of
egg allergy and eczema', say the researchers. This was explained by them as a
'gene-environment interaction' where immigrants had genes that protect against
parasite infection but increase allergy risk when growing up in a pathogen-poor
The researchers concluded -
'These findings may provide further support for a role of the hygiene
hypothesis, in combination with genetic factors, in the development of allergic
Reference: Koplin JJ, et al. Environmental and demographic risk
factors for egg allergy in a population-based study of infants. Allergy 2012;