Food avoidance doesn't prevent allergy

Telling pregnant and breastfeeding women to avoid foods such as milk, eggs and nuts does not prevent the development of allergy to those foods in their children. Results of previous research have been mixed with some studies finding decreases in dermatitis at one year. Others have found a decrease in allergy one year, but no difference at age seven. Researchers from the Pediatric Allergy and Clinical Immunology Department at the University of Manitoba conducted a trial that enrolled mothers from the Canadian Asthma and Allergy Primary Prevention study. The children were considered high risk, defined as having either one first-degree relative with asthma or two first-degree relatives with immunoglobulin E-mediated allergic disease. The researchers counselled the mothers to avoid peanuts, nuts and fish, and to decrease milk and egg consumption in the third trimester and during the first year of breastfeeding. The women were also asked to delay the introduction of solids for six months and only introduce nonhuman milk after one year, eggs after two years and nuts after three years. The researchers had parents fill out a food questionnaire before birth and at 2 weeks, and then at 2, 4, 8, 12 and 24 months. The children were given skin tests for sensitisation to milk, egg, nut, soy and wheat at one, two, and seven years of age. Data were collected from 545 families - 251 randomly assigned to the intervention group and 246 assigned to the "control" group in which no allergy avoidance measures were taken. The researchers found that at one year of age, there was no statistically significant difference between the groups. For example, about 4 percent of children in each group were allergic to milk. As many as 20 percent of the children in the intervention group and 14 percent of the control children were allergic to egg, but the differences were not significant. At two years of age, there was a significant difference between the two groups in allergy to eggs, with 12 percent of the children in the intervention group allergic to eggs but only 6 percent of controls. Four percent in the intervention group were allergic to milk, compared with only 1 percent of the control group. About 9 percent of both groups were allergic to nuts at this age. By age seven, only about 1 percent was sensitive to milk, and 1 percent to 4 percent was sensitive to eggs. At that age, 11 percent of the intervention group and 7 percent of the control group were sensitive to nuts. Hence, the overall sensitisation declined from ages one to seven. The researchers concluded that partial food avoidance strategies in the third trimester and during breastfeeding were not effective in preventing sensitisation to food among these high-risk children. On the contrary, the strategies seemed to worsen the outcome, for unknown reasons.