For decades, new parents have been told to baby-proof their home for common allergens like peanuts and pet dander. But what if you should be allergy-proofing your baby instead?
There's growing evidence to support the idea that exposing babies to allergens early on may be a legitimate way to prevent allergies later in life.
Multiple studies have shown that kids who grew up on farms or with dogs in the house are less likely to develop asthma or allergies compared with those who didn't. Earlier this year, the Learning Early about Peanut Allergy (LEAP) randomized trial found that the early introduction of peanuts into the diet of high-risk infants lowered their likelihood of being allergic to them. Other observational studies suggest the same could be possible for egg and milk, two of the most common pediatric food allergies, although no clinical trials have been done yet.
These latest results sharply contradict earlier recommendations by the American Academy of Pediatrics (AAP) to avoid feeding peanuts to high-risk children until 3 years old or later, released in 2000. Since 1997, the number of school-age children with a peanut allergy has more than quadrupled in the United States, and peanut is now the country's leading cause of food allergy-related anaphylaxis and death.
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As researchers continue
to piece together the mystery of how allergies develop -- still largely a black box -- we're seeing a major shift in prevention methods, from avoidance to early exposure. After the LEAP trial, the AAP now endorses early peanut introduction as safe and effective in infants at high risk. So how should new parents proceed? Can babies be safely exposed to peanuts, and what's the best way to introduce them into their diet?
Pediatric allergy expert Hugh Sampson, dean for translational biomedical sciences at Mount Sinai Hospital, answers these questions and more:
Q: Based on the results of the LEAP trial, how should parents proceed to prevent a peanut allergy from developing in their children?
A: The idea behind the LEAP trial came from the observation that the rate of peanut allergy in Israel was much lower than it was in Jewish kids in London. One of the big differences is the use of the Israeli snack food Bamba, which looks like a cheese doodle but contains peanut and is used as a weaning food in Israel. So these Israeli babies were getting early oral feeding of peanuts - typically when you get something orally, you become tolerant to it.
The London babies weren't getting the oral exposure which would drive tolerance, but were likely being exposed to peanut protein in the environment (e.g. house dust, hands of siblings) through their skin and therefore were more often developing peanut allergies. The LEAP trial showed that if you introduce peanut orally earlier in high-risk children, you can prevent the development of peanut allergy.
If your child represents a high-risk infant -- an infant with severe eczema or atopic dermatitis in the first few months of life, or has egg allergy in the first several months of life - he/she should be evaluated with skin-prick tests between 4 and 8 months of age to see whether or not they're already sensitized to peanuts. If they are not, they should be started on regular peanut consumption, or if only minimally sensitized, they should be given peanuts under physician supervision and then continued on regular peanut consumption because it can dramatically decrease the possibility of peanut allergy.
Q: After a negative skin-prick test and a doctor's approval, what is the best way of introducing peanut into a baby's diet?
A: Well, it depends on the age of the child. Consensus is coming around that it's better to start earlier than later -- so at 4 to 6 months of age, you might be putting a teaspoon of peanut butter into rice cereal or formula. As done in the LEAP trial and noted in our NEJM editorial: "The child should then be started on a diet that includes 2 grams of peanut protein three times a week for at least 3 years."
Also, the way Bamba is used in Israel, it is placed in the infant's mouth (at about 6 - 7 months of age) as a weaning food and just basically dissolves. So if they're old enough to have a solid in their mouth, parents in the LEAP trial would give about 21 sticks of Bamba a day, three times per week. Or an alternative would be to take the Bamba, add a little water, and make a paste.
Q: Can we apply what we know about preventing peanut allergy with early introduction to other food allergies as well?
A: That's still an open question. There was one study looking at egg allergy, where introducing egg at 4 months of age did not really prevent the development of allergy -- introduction at 4 months may have been too late. There's also an association study from Israel suggesting that children who have the least amount of milk allergy actually had milk introduced into their diet in the first couple weeks of life.
This whole concept of earlier introduction is something that's being looked at very seriously, but the final answer is not in yet. The LEAP trial is very definitive for high-risk children, but that's a subset of everybody, and whether you get the same effect in children at lower risk or whether we should be doing it in everybody is still something that has to be looked at.
Q: Why do children exposed to farms or pets grow up with fewer allergies?
A: The theory behind all this is that children living on farms or that grow up with a dog are exposed to a lot more bacteria and variety of bacteria (that we evolved with over centuries) than children who grow up in a comparatively urban sterile environment. It's very clear that the bacteria that we encounter and the bacteria that live in and on our bodies are very important for programming our immune response.
There was actually an interesting study out of Sweden where they looked at the rate of allergy in infants whose mothers would pick the binky off the floor and just lick it and give it back to the baby, as opposed to washing it carefully. Actually, the children whose mothers picked it up and licked it off had less allergies, although part of that could be because they're also getting bacteria from the mother's mouth.