Thursday, November 21, 2013

Food Allergy—Is Avoidance a Good Strategy for Prevention?

In 1998, the U.K's Department of Health decided that allergens themselves were the problem, and it recommended that infants with allergies in the family avoid known allergenic foods such as peanuts. In 2000, the American Academy of Pediatrics also issued similar guidelines.  However, A study published in the New England Journal of Medicine in 2015 turned all of this on its head—Scientists have found that avoiding peanuts to avoid an allergy is a bad strategy for most.[13]

In this article, we will address the following questions:
  • Do allergens themselves cause allergy?
  • How do we become sensitized to allergenic proteins like peanuts?

Allergy Prevention Strategy: Early Oral Exposure to Allergens

Clearly, if you had an allergy to peanuts, you should avoid them (note that emergency treatment is critical for anaphylaxis). However, avoidance failed to address the more fundamental question of how you became allergic to begin with. As a matter of fact, after officials recommended steering clear of allergens, scientists found that food avoidance failed to curb the increase in food allergies. It continued to increase in both the U.K. and U.S.

Professor Gideon Lack[1], an allergy researcher, compared the prevalence of food allergies among Jews in Israel and London, and found them to be more common in the London group—nearly 10x as common for peanuts, and 5x as high for sesames.

In Israel, infants worked out teething pains by gnawing on a peanut snack called Bamba[2]. In the U.K., however, they tended to avoid peanuts altogether. Early oral exposure to allergens—not avoidance— seemed to prevent allergy.

How Do We Become Sensitized to Peanuts?

Lack surveyed British children with peanut allergies and their parents. He could discount one theory right away—sensitization wasn't occurring prenatally. No peanut-specific antibodies showed up in blood extracted from these children's umbilical cords. He did note, however, a strong association with environmental exposure to the allergens—not orally, but through the skin. Surprisingly, he has found that:
  • Children developed food allergies because they encountered food proteins through their skin first.
    • The route of first contact mattered.

Differences between Skin and Gut

Skin is our body's largest organ. It serves as the first line of defense against intruders such as parasites or pathogens. Our immune system is probably inclined to treat foreign proteins (including proteins from peanuts or soys) it first encounters in the epidermis as intruders, and to counter with the immune response.

Proteins coming from oral route, however, is treated differently.[12] They are treated foods and are tolerated. That's how oral immunotherapy[8]—the process of deliberately training the immune system to tolerate peanuts—works. Many pathogens and parasites also approach via the oral route, but the gut immune system has ways of differentiating.

How Could Children Be Exposed to Peanuts through the Skin?

Mothers didn't know it, but some popular infant creams meant to soothe diaper rash, eczema, and dry skin contained peanut oil. Mother who used these ointments had children with a nearly 7x increased risk of peanut allergy.

What's more, certain soy proteins, it turned out, resembled proteins in peanuts. Both belonged to legume family. Some ointments contained soy products as well. Mothers using these creams could be cross-sensitizing their children to peanuts without, necessarily, sensitizing them to soy. Horribly, children with the most inflamed skin were the most likely to inadvertently sensitize them.

Feed Your Babies with Breast Milk

Parents who read this article may want to feed their infants peanuts early, say, before their kids are inadvertently sensitized to peanut proteins through their skins. However, you may want to avoid that because another baby's known condition.

Infants are born with relatively porous intestines, a natural version of what in adults we call "leaky gut syndrome." If babies are fed with foreign proteins such as peanuts, they pass right through the baby's gut and some of them are used as a nutrient while most of them, which are not found in human breast milk, are recognized as foreign substances by the part of the baby's immune system—Peyer's patches[3]. And when foreign proteins are detected, it produces powerful immune response against them.

One research has shown that food allergies have been linked to early introduction of solid foods.[11] The researchers wrote:
"Our findings suggest 17 weeks is a crucial time point, with solid food introduction before this time appearing to promote allergic disease whereas solid food introduction after that time point seems to promote tolerance."
For infants, mother's milk offers the best nourishment . As Dr Proctor[4] stated, there is a purpose for breast milk. Breast milk is an important source of gut bacteria and it also contains nutrients that feed the bugs, called prebiotics. Some breast milk compounds are actually meant to be consumed by the bugs. Also, breast milk contains crucial antibiotics.

The American Academy of Pediatrics recommends that mothers breast-feed for 12 months and the World Health Organization backs breast-feeding for up to two years. Breast-feeding a baby for 18 months to 2 years is a good way of ensuring the child's good health, especially for a strong immune system and prevention of allergies for life[5, 6].


  1. Professor Gideon Lack (Head of Department of Paediatric Allergy at King's College London)
  2. Bamba (Snack)
  3. Peyer's patch (Wikipedia)
  4. The Ins and Outs of Gut Bacteria
  5. Dietary PUFA for preterm and term infants: review of clinical studies
    • Studies report that visual acuity of breast-fed infants may be better than that of formula-fed infants.
    • Cognitive development of breast-fed infants is generally better.
  6. Breast-fed babies are more socially connected, less anxious as adults, study finds
  7. An Epidemic of Absence by Moises Velasquez-Manoff
    • An excellent book on which this article is mainly based.
  8. Red Flag Raised Over Long-term Efficacy of Oral Immunotherapy
    • "We had a high degree of optimism," senior investigator Robert Wood, MD, director of pediatric allergy and immunology at Johns Hopkins University in Baltimore, Maryland, told reporters attending a news conference. "I'm not saying we've lost that optimism, but it has certainly been tempered by looking at where these kids stand 3 to 5 years out."
  9. To Succeed At Breast-Feeding, Most New Moms Could Use Help
  10. Amish children living in northern Indiana have a very low prevalence of allergic sensitization (The Journal of Allergy and Clinical Immunology)
  11. Food Allergies Linked to Early Introduction of Solid Foods
    • The most common allergies among the children included in the study were egg allergies and cow's milk protein allergies.
  12. Pregnant Women Need Not Avoid Peanuts, Evidence Shows
  13. Avoiding Peanuts to Avoid an Allergy Is a Bad Strategy for Most

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