Canada has caught up with Europe and the United States with a new guideline advising that babies can start eating eggs, peanut butter and other potentially allergenic foods as early as six months of age – even if they are at high risk for food allergies.
The American Academy of Pediatrics published a similar guideline back in 2008. But even so, many Canadian health-care professionals have continued to follow outdated allergy recommendations, according to researchers involved in a joint statement released Monday by the Canadian Paediatric Society and Canadian Society of Allergy and Clinical Immunology.
Dr. Carl Cummings, the statement's co-author and a pediatrician in Côte Saint-Luc, Que., had no explanation for the slow uptake of newer allergy recommendations, since Canadian doctors normally follow American guidelines, he said. "The translation of medical knowledge is really a complex issue," he explained.
In the past, parents were told not to give allergenic foods such as peanuts to high-risk children before the age of 3, Cummings said. This recommendation dates to 2003 and "was based on expert opinion rather than scientific evidence," he said. In the new statement, Cummings and co-author Dr. Edmond Chan conducted a systematic review and found no evidence that delaying introduction of foods such as fish and nuts reduced the risk of developing a food allergy in babies with a family history of food allergies, asthma and atopic dermatitis. Moreover, they found no evidence showing that women should avoid eating allergenic foods while pregnant or breastfeeding to reduce food allergies in children.
For babies at high risk for food allergies, the only food to potentially avoid is baby formula containing intact cow's milk, the researchers noted. Limited evidence suggests that childhood allergy can be prevented in high-risk infants given hydrolyzed cow's milk formula in the first four to six months of life instead of intact cow's milk formula.
Food allergies affect up to 10 per cent of Canadian babies, said Dr. Stuart Turvey, an associate professor of pediatric immunology at the University of British Columbia. The rate has quadrupled in a generation – "but really we don't know why," he said.
Turvey is part of a Canadian research team involved in the government-funded Canadian Healthy Infant Longitudinal (CHILD) Study, which recruited nearly 3,500 mothers during pregnancy to study the influence of genes and the environment on healthy infant development.
According to Turvey, the "hygiene hypothesis," which has linked allergies to overly clean living environments, is a simplistic explanation for the dramatic increases in asthma, food allergies and seasonal allergies in recent decades. Turvey suggested that the spike may be due to air pollution, modern housing and a variety of lifestyle changes, including reduced contact with farm animals. "It's really a multifactorial issue," he said, noting the CHILD study data will not be published for several years.
Until more is known about allergy prevention, parents who introduce a new food to their babies are advised to continue to offer it regularly to maintain the child's tolerance for potential allergens, according to the new Canadian guideline.
In some cases, children may be less likely to develop food allergies with early introduction to a specific food. The guideline cited Australian research showing that delaying egg consumption for the first year of life resulted in a 3.4-fold increased risk of developing egg allergy, compared with introducing eggs in a child's diet between four and six months of age.
Nevertheless, the ideal time to introduce a new food may vary depending on the allergen, said Dr. Sydney Leibel, a pediatric allergist in Toronto, adding that more research is needed to know "when this window of opportunity is."
In the meantime, children who develop allergy symptoms such as hives, vomiting or diarrhea after eating a specific food should avoid that food and see a specialist for allergy testing, Leibel said.