Parents and doctors are encouraged to introduce babies safely to peanut-based foods by six months to reduce the risk of developing a peanut allergy, according to new guidelines in the U.S. and Canada.

The guidelines were released Thursday from the U.S. National Institute of Allergy and Infectious Diseases. They're based on a 2015 randomized trial that proved early introduction of peanut-based products slashed the risk of developing peanut allergy by age five among high-risk infants.

Infants are considered high risk if they are allergic to eggs, have severe eczema or both. If at high risk, parents should ask a doctor on how to proceed. The physician may want to do a test first and offer the first taste during the four-month office visit.

For other babies at low risk of allergy or moderate risk because of mild eczema, the expert panel recommends introducing foods containing peanuts at around six months.

Dr. Susan Waserman, an allergist and immunology professor at McMaster University in Hamilton, conducts research on peanut exposure as a treatment. She's been practising for about 25 years and has watched the pendulum swing on advice for preventing peanut allergies.

"There's been such a fear factor about early introduction of peanut amongst parents that it may be a hard message to sell initially," Waserman said.

While the landmark Learning Early about Peanut Allergy or LEAP study was rigorously conducted, some questions remain unanswered, Waserman said. For instance, once children have been introduced to peanut products, how long should they continue to eat them and how much?

For now, doctors advise giving the child a small amount about three times a week.

The guidelines are endorsed by the Canadian Society of Allergy and Clinical Immunology.

What kinds of foods?

Parents and caregivers should avoid feeding whole peanuts to infants because they pose a choking hazard. Instead, peanut butter, peanut flour or the peanut-flavoured puff snack Bamba can be used.

How?

Try watered-down peanut butter: Mix two teaspoons of smooth peanut butter with two to three teaspoons of hot water, and let cool.

Mix two teaspoons of smooth peanut butter with two to three tablespoons of a favourite puréed fruit or vegetable.

Mix two teaspoons of peanut flour with about two tablespoons of a favourite puréed fruit or vegetable.

Where?

For most children, those at low to moderate risk, the first feeding can be done at home, Waserman said.

Foods that might trigger allergy symptoms should be introduced when a child is free of symptoms of colds or other illnesses that could be mistaken for an allergic reaction.

What to watch for

Parents should give a small portion, then wait 10 minutes, and if there's no reaction then give the rest. They should keep watching for later reactions.

Andrea Patrick of Edmonton introduced a pinch to her first son, Beck, at 13 months of age back when the medical advice was to wait.

"He began crying immediately, his lips began to swell up and then he began to pass out and lose consciousness. That's when we really knew that something was wrong," Patrick recalled. Beck is now seven years old.

Mild symptoms to watch for include a rash or hives around the mouth or face.

By the time younger son, Marlo, 5, was born, a pediatric allergist told the family not to wait to introduce allergens.

"We were really nervous," Patrick said. "We did not want a repeat of the situation that had happened with Beck when he went into anaphylactic shock."

The new guidelines won't prevent allergies in everybody, Waserman said.

Health experts say parents should call for emergency medical help if they're home and a child suffers an anaphylactic reaction.