Posted by Brigham and Women's Hospital April 19, 2016
Contributor: Joyce T. Hsu, MD, is a food allergy specialist at Brigham and Women’s Hospital and Instructor in Medicine at Harvard Medical School.
In only the last 13 years, the prevalence of peanut allergy in the U.S. has quadrupled. Recent research, however, strongly suggests that peanut allergy – now the nation’s leading cause of food allergy-related anaphylaxis and death – can be prevented through the early introduction of peanut into a child’s diet. According to Dr. Hsu, the Learning Early about Peanut Allergy (LEAP) study may represent the key to reversing our society’s disturbing food allergy trend.
“LEAP may be the most pivotal food allergy study for our generation,” says Dr. Hsu. “Since the results were released last year, we have been trying to increase awareness about this new thinking for peanut allergy.”
The former thinking, at least in this country, says Dr. Hsu, was that parents should avoid giving their children highly allergenic foods during the first few years of life. In 2000, the American Academy of Pediatrics (AAP) recommended that children deemed to be at risk of developing food allergy not eat peanuts until the age of three. However, cases of peanut allergy continued to rise, and the AAP withdrew its recommendation in 2008.
Peanut Exposure vs. Peanut Avoidance
Suspecting that early exposure might be a better approach, a group of U.K. researchers developed a large-scale study to compare the outcomes of early exposure versus the outcomes of avoidance. More than 600 children aged four to 11 months who were identified as being at risk for developing peanut allergy – based on having severe eczema and/or an egg allergy – were enrolled in the LEAP study. All of the children were skin tested and passed an oral challenge with peanut before being divided into two groups. One group of children was assigned to eat a peanut snack several times each week until they reached the age of five, while the other group was assigned to strictly avoid peanut consumption. The study found that regular peanut consumption, as compared to peanut avoidance, reduced the risk of developing peanut allergy by more than 80 percent.
For the LEAP-ON follow-up study, researchers followed the original consumption and avoidance groups after they were directed to forego peanuts for an entire year (from age five to age six) immediately after the end of the initial study. This resulted in only a nominal increase in peanut allergy development among both groups, demonstrating, says Dr. Hsu, that early exposure has some lasting effect.
Applying the Evidence
Based on the evidence gleaned from the LEAP and LEAP-ON studies, an increasing number of allergy clinics, including Dr. Hsu’s, are recommending that children at risk for peanut allergy be tested for peanut sensitization, preferably before one year of age. Infants who have a negative or mild reaction to the test should then be given an oral food challenge, while children who experience a strong skin reaction should continue to avoid eating peanuts.
The challenge is usually done in three steps, says Dr. Hsu, all in one clinic visit over the course of several hours. The child is given increasing doses of peanut butter – ¼ teaspoon, ½ teaspoon, 2 tablespoons – with the physician monitoring the response after each dose. If the child has no adverse reaction after ingesting the two-tablespoon dose, parents are asked to give the child two tablespoons of peanut butter daily over the next three days. If the child continues to do well, they should continue to eat peanut protein regularly over the next few years – at least two tablespoons of peanut butter per week is recommended.
Dr. Hsu stresses that the initial testing and challenges should be done in the controlled environment of a clinic to ensure the child’s safety.
“We recommend that kids have the testing and oral challenge in the allergy clinic,” she says. “It’s the first introduction of peanuts for almost all of these kids, so you really want to monitor them closely.”
Implications for Other Food Allergies
Dr. Hsu and her colleagues are now discussing what the LEAP findings mean for other common food allergens. Many specialists believe that early introduction for other highly allergenic foods may be a good idea, but there are no guidelines yet for foods other than peanut.
“We know that when we avoid introducing peanut to children, the likelihood of developing a peanut allergy seems to increase,” says Dr. Hsu. “It is possible that the same is true for other food allergies.”
To schedule a consultation with an allergist at the Brigham and Women’s Health Care Center in Chestnut Hill, call (617) 732-9850, and for an allergist at Brigham and Women’s/Mass General Health Care Center in Foxborough, please call (508) 718-4000.
– Chris P.