What's behind a rise in childhood allergies, and can anything be done to prevent it? Sydney-based gastroenterologist Dr Vincent Ho, has written a new book called The Healthy Baby Gut Guide which looks at what parents can do to help babies develop strong immune responses in their first 1000 days.

Although serious food allergies are on the rise, parents can a build a child's food allergy tolerance even before birth, a Sydney-based gastroenterologist says.

Dr Vincent Ho's new book The Healthy Baby Gut Guide looks at what parents can do to help babies develop strong immune responses in their first 1000 days.

Listen to the full interview

He tells Kathryn Ryan there are several ways parents can minimise the risks of childhood food allergies and that diversity of gut microbes from an very early age plays a huge part. Many allergies are on the rise, recent figures show.

"The big four allergies are eczema, food allergies, asthma and allergic conjunctivitis, that used to be known as hayfever," he says. "We know that all of these allergies are on the rise and in fact, both in Australia and New Zealand, we know that the prevalence for asthma is extremely high in children."

Statistics collected by the Ministry of Health identified a rise in the very severe food reaction anaphylaxis.

It is a potentially life-threatening reaction with numerous potential causes, with food allergy being the leading cause in children.

New Zealand figures, from 2002-2011, also found that seafood was the most common cause anaphylaxis followed by nuts.

"We know that with an immune reaction what happens is when a foreign substance is viewed as a threat by the body the body sets up a number of processes, including the production of antibodies to target that particular substance. What that can led to in some individuals is a very profound reaction.

"As part of that allergy is itchy skin and swelling, but what can also in some cases can be a more profound reaction like sudden drop in blood pressure due to the swelling of blood vessels. There can be respiratory issues like difficulty in breathing. All of those symptoms are really life-threatening and so when anaphylaxis occurs... it must be treated immediately."

A common treatment is the administration of adrenaline.

Not all food allergies are the same and many children stop becoming allergic to certain foods as they enter adulthood, he says. But not all foods.

"We know that nine food allergies cause about 90 percent of all food allergies and... the ones children can outgrow are egg, wheat, soya and dairy..…

Go to this episode on rnz.co.nz for more details