May 2013 Issue

Outgrowing Food Allergies — Evidence Shows Multiple Factors Affect Outcome
By Sherry Coleman Collins, MS, RD, LD
Today’s Dietitian
Vol. 15 No. 5 P. 12

More than one-quarter of US children with a history of food allergies outgrow their sensitivities. However, according to a preliminary study presented at the recent American College of Allergy, Asthma, and Immunology (ACAAI) annual meeting, some children take longer to outgrow them compared with those in previous generations.1

It’s unknown why some children develop a tolerance to food allergens while others continue to suffer from them into adulthood. Researchers speculate that multiple allergies, the types of allergenic proteins, and a diet of strict avoidance vs. gradual introduction of the offending foods may play a key role.

Multiple Food Allergies
According to Ruchi Gupta, MD, MPH, lead study researcher, nearly one-third of the children with food allergies who participated in an electronic survey of more than 40,000 households had multiple food allergies, which may be one reason it appears as though they’re outgrowing their allergies at a later age.

“Children with multiple food allergies are known to outgrow their allergies less frequently, and these children often have associated severe eczema, asthma, and rhinitis,” says Gideon Lack, MD, FRCPCH, a professor of pediatric allergy at King’s College London. “Overall they’re likely to have an immune response toward allergic inflammation [a Th2 response]. It may be harder to reverse this extreme response.” Th2 refers to a type of T lymphocyte that controls the release of cytokines. For people with allergies, including food allergies, an exaggerated Th2 response can result in a more severe reaction and persistent allergy.2

Food Proteins
The type of protein causing the allergic reaction can be an important factor in whether children outgrow food allergies earlier rather than later. Researchers are examining how allergenic proteins with different structures adhere to cells and cause reactions. It’s believed that some food proteins are more resistant to being denatured, possibly making them more allergenic.

For example, Gupta’s study showed that 41% of milk, 40% of egg, 16% of peanut, and 13% of shellfish allergies were outgrown. Children were most likely to outgrow tree nut allergies by the age of 10, and shellfish allergies by the age of 12, according to Medscape. In addition, 55% of children with an egg allergy and 45% with a milk allergy outgrew their symptoms by the age of 6 or 7. Gupta reported that most children will outgrow their allergies by the age of 10, but tolerance can develop at any age.

Other research concurs with Gupta’s. Skolnick and colleagues studied individuals between the ages of 4 and 20 (median age of 6) with a peanut allergy and found that approximately 21.5% outgrew their peanut allergy.3 Keet and colleagues found that 65% of children outgrow their wheat allergy by the age of 12.4 Fleischer and colleagues determined that about 9% of children outgrow tree nut allergies and recommended that those aged 4 or older be retested.5

Strict Avoidance vs. Gradual Introduction
Strictly avoiding allergenic foods has been an important strategy for protecting against allergic reactions, since even the smallest amount of an offending protein can cause symptoms to flare. However, this may prevent “natural immunotherapy,” whereby children are exposed to tiny amounts of food proteins over time so they can build tolerance. Some researchers have found that children are prone to outgrow certain allergies more quickly than others because they’re consistently exposed to the protein.

“It may be that it’s easier to outgrow an egg and milk allergy because the allergens are less stable in heat and while cooking,” Lack says. “Therefore, children are inevitably exposed to small amounts of baked egg and milk ingredients without reacting. This may desensitize them over time.”

Some allergists allow children with egg allergies to eat baked goods containing eggs in the office setting to help facilitate this process. This has been achieved successfully in previous studies and recent research presented at the ACAAI meeting by Rushani Saltzman, MD, an allergist at the Children’s Hospital of Philadelphia’s Pediatric & Adolescent Specialty Care Center. Saltzman’s study showed that when children with an egg allergy ate a baked product containing egg, more than 50% tolerated it.6 As a result of this and other research, strict avoidance of food allergens in infancy and early childhood as a means of preventing allergies has been called into question.

The American Academy of Pediatrics and other organizations now state that the research doesn’t support avoiding potential food allergens beyond 4 to 6 months of age as a strategy to prevent food allergies.7 In fact, recent research by DuToit and colleagues indicates that an earlier introduction to peanuts may provide protection against the development of a peanut allergy.8 In his current clinical trial, Learning Early About Peanut Allergy (LEAP Study), Lack is studying more than 600 children to determine the difference between early vs. delayed introduction in the development of a peanut allergy.9

Is It Possible to Induce Tolerance?
Many questions remain about how food allergies develop and what factors may increase or mitigate the risk of development. Once a food allergy is diagnosed, however, many patients and their families want to know how they might reverse it or develop tolerance. Research is ongoing worldwide to determine how to induce tolerance. In the United States, researchers are using oral and sublingual immunotherapy.

Oral immunotherapy involves oral feeding of small and increasing amounts of the allergen to subjects over time, while sublingual immunotherapy involves placing small and increasing amounts of the allergen under the tongue over time. Clinical trials have found oral and sublingual immunotherapy to be effective in some subjects, while others have been unable to tolerate treatment because of significant adverse reactions.

In some cases, an individual’s food allergy has returned when he or she didn’t consume the allergenic protein after a period of time. This suggests study participants didn’t achieve true tolerance and that researchers observed only a period of nonreactivity. Clearly, more research is needed to determine whether tolerance can be induced before making oral or sublingual immunotherapy available in the office setting.

Diagnosis, Management, and Reevaluation
An expert panel established by the National Institutes of Allergy and Infectious Diseases published guidelines in 2010 to help create standards of practice for proper diagnosis, management, and treatment of food allergies.10 The report discussed the importance of retesting and reevaluation as an integral part of care, since individuals can outgrow their allergy at any age.

The guidelines state that physicians should request follow-up testing and adhere to recommendations to reintroduce allergenic foods into their patients’ diets.10 However, because of a lack of available research, the guidelines don’t indicate how frequently physicians should perform allergy testing. The recommendations say testing should be determined based on the child’s age, allergen in question, severity of the reaction, and how recently the reaction occurred. Current practice includes more frequent testing for milk and egg allergies, and less frequent testing for peanut, tree nut, and seafood allergies, although this isn’t based on specific evidence.

Oral food challenges are the gold standard for diagnosing a food allergy and can be an important part of retesting when clinical and physical indications suggest they can be safely used. Retesting and following a child’s history is an important part of determining when he or she may be able to safely reintroduce the food allergen back into his or her diet.

Nutrition professionals can be an important part of the interdisciplinary health care team by doing the following:

• applying the nationally recognized guidelines for food allergy diagnosis and management;

• counseling clients and patients about the importance of retesting and reevaluations to determine if they’ve outgrown their food allergy;

• helping clients and patients learn skills to safely avoid allergens in foods; and

• ensuring clients and patients eat a variety of nutritious foods that are enjoyable and safe.

Nutrition professionals working in the area of food allergy management should remain abreast of the changing research and guidelines, recognizing that a food allergy diagnosis has the potential to change over time. Food allergy diagnosis, treatment, and management are dynamic areas of practice where dietitians can make a difference in the lives of their clients and patients.

— Sherry Coleman Collins, MS, RD, LD, has worked in clinical pediatrics and school foodservice, where she gained hands-on experience working with students, families, and staff to manage food allergies. She’s currently the senior manager of marketing and communications for the National Peanut Board.

 

Why Are Food Allergies on the Rise?
Currently, more than 15 million Americans, including millions of children, suffer from food allergies. Between 1997 and 2007, food allergies increased 18%, according to the Centers for Disease Control and Prevention. Researchers aren’t sure why the prevalence of food allergies has increased, but several theories exist.

The hygiene hypothesis suggests that because of better sanitation and cleanliness, our immune systems mistake food proteins for foreign bacteria, viruses, and parasites, resulting in an attack against them. Some say the modern diet, which includes the consumption of genetically modified organisms in food, may play a part, although this theory isn’t well supported in the literature.

Others say vitamin D deficiency plays a role. According to a study published online in March in the Journal of Allergy and Clinical Immunology, infants with vitamin D deficiency were more likely to have peanut and egg allergies and multiple food allergies than those with adequate vitamin D levels.

Finally, the protocol for diagnosing food allergy, when inappropriately followed, can lead to false-positives.

— SCC

 

References
1. Painter K. Food allergies outgrown by more than one in four kids. USA Today website. http://www.usatoday.com/story/news/nation/2012/11/10/food-allergies-outgrown/1695451. Accessed March 24, 2013.

2. Berger A. Th1 and Th2 responses: what are they? BMJ. 2000;321(7258):424.

3. Skolnick HS, Conover-Walker MK, Koerner CB, Sampson HA, Burks W, Wood RA. The natural history of peanut allergy. J Allergy Clin Immunol. 2001;107(2):367-374.

4. Keet CA, Matsui EC, Dhillon G, Lenehan P, Paterakis M, Wood RA. The natural history of wheat allergy. Ann Allergy Asthma Immunol. 2009;102(5):410-415.

5. Fleischer DM, Conover-Walker MK, Matsui EC, Wood RA. The natural history of tree nut allergy. J Allergy Clin Immunol. 2005;116(5):1087-1093.

6. An egg a day to keep allergies away. American College of Allergy, Asthma, and Immunology website. http://www.acaai.org/allergist/news/New/Pages/AnEggaDaytoKeepAllergiesAway.aspx. Accessed March 3, 2013.

7. Greer FR, Sicherer SH, Burks AW, Committee on Nutrition and Section on Allergy and Immunology. Effects of early nutritional interventions on the development of atopic disease in infants and children: the role of maternal dietary restriction, breastfeeding, timing of introduction of complementary foods, and hydrolyzed formulas. Pediatrics. 2008;102(1):183-191.

8. DuToit G, Katz Y, Sasieni P, et al. Early consumption of peanuts in infancy is associated with a low prevalence of peanut allergy. J Allergy Clin Immunol. 2008;122(5):984-991.

9. Background on the LEAP study. LEAP website. http://www.leapstudy.co.uk/LEAP.html. Accessed March 3, 2013.

10. NIAID-Sponsored Expert Panel, Boyce JA, Assa’ad A, et al. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. J Allergy Clin Immunol. 2010;126(6 Suppl):S1-S58.

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