Scientists believe the babies are left vulnerable by avoiding the journey through the birth canal, which would normally expose them to their mother’s bacteria.
The discovery lends support to the 'hygiene hypothesis' that links childhood allergy to over-clean conditions early in life.
Lead researcher Dr Christine Cole Johnson, from the Henry Ford Hospital in Detroit
, in the U.S., said: 'This further advances the hygiene hypothesis that early childhood exposure to micro-organisms affects the immune system’s development and onset of allergies.
'We believe a baby’s exposure to bacteria in the birth canal is a major influencer on their immune system.'
Dr Johnson’s team studied 1,258 newborn babies and assessed them when they were one month, six months, one and two-years-old.
By two years of age, babies born by C-section were much more likely to have developed allergies to triggers in the home such as the droppings of house dust mites, and dander, or dead skin, shed by dogs and cats.
Umbilical cord and stool samples from each baby were analysed, together with blood samples from both parents, breast milk and household dust.
Information was also collected on every family’s history of allergy or asthma, household pets, tobacco smoke exposure, baby illnesses, medication use, and aspects of pregnancy.
The results of the research were presented today at the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Antonio, Texas.
C-Sections Unhealthy For Mother and Baby
A Danish study examining 34,000 deliveries suggests babies born by C-section were up to four times more likely to have respiratory problems than those born naturally.
Newborns delivered by caesarean may miss out on critical bacterial molecules that help their gut grow healthily--something that seems to be effectively accomplished through vaginal births.
A recent study also showed that caesarean born babies are also at double the risk of becoming obese children as those delivered naturally.
Infants who are delivered by C-section may have an increased risk of developing food allergies, according to a new report published in the August issue of the Journal of Allergy and Clinical Immunology.
Women who have their first child by caesarean are also more likely to have placenta-related problems in their second pregnancy, research suggests. A Caesarean section increases the risk by 50-fold that a woman's uterus will rupture during a subsequent vaginal delivery, research suggests.
Women who give birth by caesarean section take longer on average to become pregnant again, according to the results of a large British study
Women having a non-emergency caesarean birth have double the risk of illness or even death compared to a vaginal birth, according to a study from Latin America.
Each year the number of allergy sufferers in theby 5 percent, half of whom are children.
Ten percent of children and adults under the age of 45 have two or more allergies.
Maureen Jenkins, director of clinical services at the charity Allergy UK, said: 'During a natural birth the baby travels slowly down the birth canal where it ingests normal bacteria, which has been shown to aid a healthy immune response and protect against allergy.
'In the case of a Caesarean section, the baby has no contact with the birth canal. Instead it is immediately removed from a sterile environment, meaning the chances of developing allergy could be heightened.'
Karen Foster is a holistic nutritionist, avid blogger, with five kids and an active lifestyle that keeps her in pursuit of the healthiest path towards a life of balance.