To reduce the risk of peanut allergy, infants should eat foods containing peanuts by the time they are six months old, according to new guidelines released Thursday by a U.S. government panel.

The recommendation marks a dramatic evolution in the scientific understanding of how peanut allergy develops. Instead of delaying peanut exposure in infancy, as earlier guidelines recommended, "you should actively introduce peanut," said the panel's Canadian member, Edmond Chan, head of the division of allergy and immunology at the University of British Columbia's department of pediatrics and director of the allergy clinic at BC Children's Hospital.

Caution about feeding foods containing peanuts to infants "has probably led to more peanut allergies," Dr. Chan said.

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The U.S. National Institute of Allergy and Infectious Diseases set up the panel after the 2015 release of results from a landmark study. The Learning Early about Peanut Allergy (LEAP) trial showed that the early introduction of peanuts among infants at high risk of peanut allergy dramatically reduced their risk of developing the allergy by the age of 5. Other studies looking at foods such as eggs support the early introduction of specific allergenic foods, Dr. Chan said.

In the LEAP study, just seven out of 319 high-risk infants reacted to peanut after their first oral exposure to it under medical supervision. Of those, Dr. Chan pointed out, "none of them were anaphylactic [a life-threatening allergic reaction]."

He added that in Israel, where the prevalence of peanut allergy is low, parents typically feed peanut products to their children in infancy, including a widely consumed peanut-butter-flavoured snack called Bamba.

The risk of a life-threatening allergic reaction is higher if a child eats peanut for the first time at around one year of age, he said, "but that's another reason to introduce it as early as possible."

Children at high risk for peanut allergy – those with severe eczema or egg allergy – should consume foods containing peanuts by four to six months of age, but only after being tested by a medical professional for a possible allergic reaction, the panel said. Infants at low to moderate risk don't need to be tested beforehand.

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Severe eczema in infancy is a greater risk factor than a family history of peanut allergy, Dr. Chan said. Researchers hypothesize that infants with eczema have a broken skin barrier, which provides a portal of entry for food allergens. Skin contact may trigger an allergic response that persists when an infant eats foods containing peanuts. But if an infant eats peanut early in life, the gastrointestinal tract has a chance to develop tolerance, "so that's good exposure," Dr. Chan said.

After their first taste of peanut, all infants – regardless of allergy risk – should consume peanut products a few times a week. To reduce an infant's risk of choking on peanuts, the guidelines suggest mixing peanut butter with pureed fruits and vegetables, dissolving peanut butter in water or adding peanut flour to mashed-up foods. (Details about how to introduce peanut to infants are available in the appendix to the guidelines, published online in several medical journals, including the Canadian journal Allergy, Asthma and Clinical Immunology.)

Dr. Chan said it may take time to change the public mindset about feeding peanut to infants because "there's been this fear factor."

Rates of life-threatening peanut allergy have increased over the past two or three decades. In 2000, the American Academy of Pediatrics (AAP) recommended that children at high risk of peanut allergy should not eat peanut before the age of 3. In 2008, the AAP changed the guidelines, saying there was no benefit in delaying exposure to peanut beyond six months of age. A 2013 position paper from the Canadian Paediatric Society echoed the AAP's 2008 guidelines and noted that the protective effect of early introduction of potentially allergenic foods "remains under investigation."

Nevertheless, health-care professionals have been slow to act on the changing recommendations.

In 2013, Dr. Chan surveyed pediatricians in Atlantic Canada and found that more than 80 per cent were recommending that babies avoid foods containing peanuts until their first birthday.

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"I can understand parents' fears – they hear about children having severe reactions, or about parents having to carry EpiPens, and figure that it's better to be safe than sorry," Dr. Chan said in a news release. "But the safer thing to do, for almost all infants, is to feed them peanut by the sixth month and then give it regularly thereafter."