Truth or Fiction: Risk Factors for Childhood Atopic Dermatitis
January 2012 | Volume 11 | Issue 1 | Feature | 126 | Copyright © 2012
Kendra Gail Bergstrom MD
Atopic dermatitis is increasing in prevalence throughout the developed world, in parallel with asthma and hay fever. The reasons for the increase remain unclear. As a practical question, it is valuable to understand which interventions might decrease risk for childhood atopic disease. Prospective studies among infants and children are challenging to design and to execute. Fortunately, several large studies from Europe and the United States are better characterizing whether behavioral interventions such as breastfeeding, delayed introduction of solid foods, hydrolyzed protein infant formulas, or pets in the home might be protective or impart increased risk of developing atopic dermatitis. As this body of literature grows, physicians will be able to recommend behavioral interventions that can prevent atopic dermatitis in individuals and ideally decrease prevalence over the population.
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Prevalence of Atopic Dermatitis
The prevalence of atopic dermatitis has been increasing in Western societies over the past 30 or more years, and the overall prevalence in children is estimated at 10-20 percent.1 In parallel, the incidence of asthma has increased from three percent to five percent over a 20-year period.2 The concept of the “atopic march” postulates that early intervention into atopic dermatitis, in addition to helping a child's skin stay healthy, may delay or prevent the development of asthma in children.
There are several challenges to studying risk factors for infantile atopic dermatitis. Many studies are retrospective, inviting risks of recall bias among mothers. For prospective studies, many mothers are hesitant to enroll their children in experimental protocols. Ideally, a study could monitor an early intervention such as breastfeeding or diet changes, and follow these infants for several years into childhood and adolescence. Studies of this scope are unfortunately expensive and take several years to complete.
Against the background of increasing atopic dermatitis incidence in infants and children, the push for preventative strategies for mothers and families continues. Several behavioral and environmental risk factors have been identified, and interventions have been attempted among infant and pediatric populations. While some interventions have proved less helpful—maternal dietary restriction and maternal ingestion of prebiotics (carbohydrates that promote growth of gastrointestinal flora)—others appear to be helpful. Highlights from the latest literature are reviewed in Table 1.
The overall beneficial effects of breastfeeding on infant health are well-established. In 2008, based on incomplete but promising data, the American Academy of Pediatrics recommended exclusive breastfeeding for at least four months to protect high-risk infants from eczema over the first two years of life.3
Since that time, the largest study to date4 followed over 51,000 children ages 8-12 years in 21 different affluent and non-affluent countries to determine the relationship between breastfeeding and eczema diagnosis. Breastfeeding time frames were classified as less that two months, two to four months, and over four months. Among these children, breastfeeding had no protective effect. In fact, eczema risk was moderately increased in children who had been breastfed over those who had not. The increase was particularly striking in children from affluent countries who were diagnosed with eczema before the age of two. The authors of the above study postulate that the increase in eczema in breastfed infants might be due to a selection bias: mothers deciding to breastfeed their infants because of a family history of eczema.
The overall benefits of breastfeeding are well-established, but whether these extend to protection from atopic dermatitis is unclear. Several case reports and case-control studies suggest protection from infantile asthma and atopic dermatitis as well. This benefit had not been established in larger studies prior to the most recent publication in 2011. One challenge is the length of time infants are followed after their period of breastfeeding; while breastfeeding may be protective over the first year, there is conflicting evidence as to whether these benefits persist into early childhood or into teenage years.
Maternal diet during pregnancy and lactation does not seem to affect the onset of atopic eczema. Previous hypotheses that a mother's ingestion of peanuts during pregnancy or lactation can lead to peanut allergy have since been dispelled.
Hydrolyzed Infant Formula
When breastfeeding is not possible, the question arises as to whether some types of baby formulas are more likely to be protective against atopic disease. “Regular” baby formulas contain larger protein molecules from cow's milk like casein, soy, or whey. Ingesting large protein molecules could theoretically trigger a food allergy, which may be associated with atopic dermatitis or with asthma. Fortunately, the protein molecules can be broken down into smaller particles which are less likely to be allergenic. While not done routinely for baby formula, several brands of baby food offer so-called “elemental” or “hydrolyzed” formula with whey protein molecules broken down into smaller sizes. Alimentum, Nutramigen, and Pregestimil are among brands of hydrolyzed formulas, while Neocate, Elecare, and