Exposure to animals from infancy will reduce the risk of allergies and asthma, according to immunologist Luke O’Neill. 

A “striking” study on more than 65,000 infants in Japan found that children exposed to pet cats or indoor dogs during fetal development or early infancy developed fewer food allergies than other children.  

“What's happening is the infant - or the mother while she’s carrying - is picking up germs off the dog,” Prof O’Neill told The Pat Kenny Show.  

“Those germs are training the immune system in the foetus - and then in the new-born - to behave itself and not overreact.” 

This study agrees with the ‘hygiene hypothesis’ that bacterial germs are good for the immune system, according to Prof O’Neill. 

“German scientists in 1980s noticed that if there was small number if kids in the family, there was an increased risk of developing an allergy,” he said.  

“The only child household has a higher risk of developing asthma.” 

Bacteria vs viruses 

Prof O’Neill said the hygiene hypothesis only applies to bacterial germs as opposed to viral germs.  

“Every case of a viral infection increases the chance of allergy,” he said.  

The immunologist said that the most common exposure is likely vaporised poo.

The exposure to bacteria on farms in particular “train your immune system to learn good from bad”. 

Caesarean section 

Prof O’Neill also said that a caesarean section is “a risk factor for developing allergies and asthma”. 

“The foetus is not exposed to bacteria when being born through the birth canal,” Prof O’Neill said, “The child is off to a slight disadvantage.” 

According to the immunologist, 8% of children have some form of allergy now, which is “the highest it’s ever been”. 

Prof O’Neill recommended a fibre diet to avoid allergies as you process your food better and are exposed to “the good bacteria”.