TY - JOUR
AU - Wood, Robert A.
AB - One of the great controversies in pediatric allergy during the past 2 decades has been and remains the potential to prevent the development of allergy and asthma. The controversy stems largely from the lack of quality studies and conflicting data from the few studies that have been done; some studies have demonstrated significant protection and most others have shown little or no effect. Possible approaches to allergy prevention include maternal dietary restrictions during pregnancy, breastfeeding, dietary restrictions while breastfeeding, the use of hypoallergenic infant formulas, and delays in the introduction of foods into the infant's diet, both in general and specifically in regard to more allergenic foods.1 In addition, the use of probiotics or other immunomodulatory agents and the avoidance of environmental allergens and irritants, such as tobacco smoke, have been suggested as possible approaches to allergy prevention. The apparently rapid increase in the prevalence of allergic disease during the past few decades compels us to consider anything that might stem this rising tide, although it should be equally compelling to avoid recommendations that are not grounded in science. The hesitancy to make unfounded recommendations is particularly important because all of these suggested approaches require substantial education and motivation on the part of the family; most are inconvenient, many are costly, and some may place infants and mothers at significant nutritional risk. Among these possible approaches, delaying the introduction of solid foods into the infant's diet is one of the most commonly recommended. As with most of these recommendations, this one was based on a few studies that suggested benefit without questioning their validity, and based on largely ignoring other negative studies. We are therefore indebted to Tarini and colleagues2 for their excellent review of this topic in this issue of the ARCHIVES. In the review by Tarini et al, a total of 13 studies were identified that met their inclusion criteria, only one of which was a controlled trial. Five of these 13 studies found a positive association between early solid feeding and eczema, while 4 found no such association. None of the studies provided strong evidence to support the association between early solid feeding and the development of persistent food allergy, persistent asthma, or allergic rhinitis. Therefore, they concluded that early solid feeding may increase the risk of eczema but that there is little data supporting an association. As with most studies regarding allergy prevention, they recommended that additional controlled trials be performed to provide sound advice to physicians and families regarding the timing of solid food introduction. Given this degree of uncertainty, what then should we be recommending to our patients? The first decision is whether a recommendation should be made globally, that is, to all families regardless of their atopic predisposition or whether it should be reserved for those with a higher risk of developing allergies. Although asthma and allergies commonly occur in children from families without any history of allergic disease,3,4 a careful family history remains the most simple and effective tool to screen for atopic risk. At this point, most prevention strategies are best reserved for children at higher risk of developing allergies, at least until more definitive strategies can be recommended. There are probably only 2 measures that should be universally recommended, breastfeeding and the avoidance of environmental tobacco smoke. Environmental tobacco smoke exposure, especially during pregnancy and infancy, clearly increases the risk of childhood allergy and asthma.5-7 Although no study has proven that environmental tobacco smoke avoidance is beneficial, it is still logical to advise avoidance of environmental tobacco smoke exposure. With regard to dietary measures, exclusive breastfeeding should be recommended first and foremost. However, this is not meant to imply that breastfeeding has been conclusively shown to prevent allergy. While some studies have demonstrated protection,8,9 others have failed to do so.10,11 Two meta-analyses on this subject concluded that exclusive breastfeeding does seem to have some protective effect on the development of allergy,12,13 and given the other benefits of breastfeeding, there is little doubt about this recommendation. As for other dietary measures, the recommendations are less clear. Maternal avoidance of allergenic foods during pregnancy has not been shown to be helpful,14 although there is evidence that sensitization may begin in utero and many experts still recommend that at least peanut and tree nuts be avoided in the maternal diet during pregnancy. Maternal avoidance of allergenic foods during lactation, particularly milk, egg, and peanut, has been studied extensively without conclusive results, but a general notion that while there may be a preventative effect in the first 1 to 2 years of life, there is not likely to be any longer-term benefit.15,16 In addition, these avoidance diets during pregnancy and lactation may put mothers and infants at nutritional risk and should only be considered for highly motivated families with a high risk of allergy. The use of hydrolyzed infant formulas as a preventative measure has also been studied extensively. Most studies have shown that extensively hydrolyzed formulas are clearly superior to cow's-milk formulas and some have shown that partially hydrolyzed formulas might be as or even more effective than extensively hydrolyzed products.17-20 This approach has not been shown to be superior to exclusive breastfeeding, but may make sense as a supplement to breast milk in high-risk infants. The final dietary strategies involve the delay in food introduction to the infant and toddler. As noted previously, convincing proof for the preventive effects of the delayed introduction of solid foods is lacking. It has also been suggested that certain allergenic foods, such as milk, egg, and peanut, be withheld from the diet of at-risk children. In fact, a current position statement from the American Academy of Pediatrics recommends withholding milk until age of 1 year, egg until age of 2 years, and peanut, tree nuts, and fish until age of 3 years in high-risk infants.21 It should also be noted, however, that there is little evidence to support these recommendations and a similar position statement from the European Societies for Paediatric Allergology and Clinical Immunology and Paediatric Gastroenterology, Hepatology, and Nutrition makes no such recommendation.22 Other potential approaches that have been studied with mixed results include the avoidance of house dust mites and other environmental allergens,23-25 the use of probiotics and other immunomodulatory agents,26-29 and certain medications.30 There is some evidence that each of these approaches might have some effect, but none appear to be long lasting. For example, probiotics have been shown to potentially reduce early atopic dermatitis, but convincing data on the prevention of food and other allergies is currently lacking. This is an area of active research, however, that we will be hearing more about in the next few years. Given these limited and often conflicting data, how should we proceed? Is this really a losing battle or a battle still worth fighting? Families with affected children are often intensely committed to reduce allergy in subsequent children and should certainly be provided with this information. We need to be careful when providing information, however, without being dogmatic given the current state of knowledge. In the long run, I remain extremely optimistic that some combination of these, and potentially other new strategies, will have a significant impact on the rising tide of allergic disease. Correspondence: Dr Wood, Johns Hopkins University, 600 N Wolfe St, Baltimore, MD 21287 (rwood@jhmi.edu). References 1. Arshad SH Primary prevention of asthma and allergy J Allergy Clin Immunol 2005;1163- 14PubMedGoogle ScholarCrossref 2. Tarini BACarroll AESox CMChristakis DA Systematic review of the relationship between early introduction of solid foods to infants and the development of allergic disease Arch Pediatr Adolesc Med 2006;160502- 507Google ScholarCrossref 3. Bergmann RLEdenharter GBergmann KE et al. Predictability of early atopy by cord blood-IgE and parental history Clin Exp Allergy 1997;27752- 760PubMedGoogle ScholarCrossref 4. Bergmann RWoodcock A Whole population or high-risk group? Childhood asthma Eur Respir J Suppl 1998;279s- 12sPubMedGoogle Scholar 5. Jaakkola JJGissler M Maternal smoking in pregnancy, fetal development, and childhood asthma Am J Public Health 2004;94136- 140PubMedGoogle ScholarCrossref 6. 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Wright ALHolberg CJTaussig LMMartinez FD Factors influencing the relation of infant feeding to asthma and recurrent wheeze in childhood Thorax 2001;56192- 197PubMedGoogle ScholarCrossref 11. Sears MRGreene JMWillan AR et al. Long term relation between breast feeding and development of atopy and asthma in children and young adults: a longitudinal study Lancet 2002;360901- 907PubMedGoogle ScholarCrossref 12. Gdalevich MMimouni DMimouni M Breast-feeding and the risk of bronchial asthma in childhood: a systematic review with meta-analysis of prospective studies J Pediatr 2001;139261- 266PubMedGoogle ScholarCrossref 13. Mimouni Bloch AMimouni DMimouni MGdalevich M Does breastfeeding protect against allergic rhinitis during childhood: a metaanalysis of prospective studies Acta Paediatr 2002;91275- 279PubMedGoogle ScholarCrossref 14. Falth-Magnusson KKjellman NI Allergy prevention by maternal elimination diet during late pregnancy: a 5-year follow-up of a randomized study J Allergy Clin Immunol 1992;89709- 713PubMedGoogle ScholarCrossref 15. Zeiger RSHeller SMellon MH et al. Effect of combined maternal and infant food-allergen avoidance on development of atopy in early infancy: a randomized study J Allergy Clin Immunol 1989;8472- 89PubMedGoogle ScholarCrossref 16. Zeiger RSHeller S The development and prediction of atopy in high risk children: follow-up at age seven years in a prospective randomized study of combined maternal and infant food allergen avoidance J Allergy Clin Immunol 1995;951179- 1190PubMedGoogle ScholarCrossref 17. von Berg AKoletzko SGrubl A et al. The effect of hydrolyzed cow's milk formula for allergy prevention in the first year of life: the German Infant Nutritional Intervention Study, a randomized double-blind trial J Allergy Clin Immunol 2003;111533- 540PubMedGoogle ScholarCrossref 18. Halken SHansen KSJacobsen HP et al. Comparison of a partially hydrolyzed infant formula with two extensively hydrolyzed formulas for allergy prevention: a prospective, randomized study Pediatr Allergy Immunol 2000;11149- 161PubMedGoogle ScholarCrossref 19. Ram FSDucharme FMScarlett J Cow's milk protein avoidance and development of childhood wheeze in children with a family history of atopy Cochrane Database Syst Rev 2002;3CD003795PubMedGoogle Scholar 20. Hays TWood RA A systematic review of the role of hydrolyzed infant formulas in allergy prevention Arch Pediatr Adolesc Med 2005;159810- 816PubMedGoogle ScholarCrossref 21. American Academy of Pediatrics, Committee on Nutrition: hypoallergenic infant formulas Pediatrics 2000;106346- 349PubMedGoogle ScholarCrossref 22. Host AKoletzko BDreborg S et al. Dietary products used in infants for treatment and prevention of food allergy. 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TI - Prospects for the Prevention of Allergy: A Losing Battle or a Battle Still Worth Fighting?
JF - Archives of Pediatrics & Adolescent Medicine
DO - 10.1001/archpedi.160.5.552
DA - 2006-05-01
UR - https://www.deepdyve.com/lp/american-medical-association/prospects-for-the-prevention-of-allergy-a-losing-battle-or-a-battle-TMl7O6tJv6
SP - 552
EP - 554
VL - 160
IS - 5
DP - DeepDyve
ER -