Many patients with eczema go on to develop food allergies, a phenomenon often referred to as “the allergic march.” But the exact relationship between the two diseases has so far been unclear. Lately, however, the theory that food proteins slip in through the compromised skin barrier of a child with eczema, leading to sensitization and predisposing him to food allergies, has gained ground.
New research out of National Jewish Health in Denver, presented at the AAAAI meeting in March, bolsters that theory and points specifically to the staphylococcus aureus bacteria, present on the skin of about 50 percent of patients with eczema, as a potential culprit in the skin breakdown that leads to the development of food allergies.
“Staph aureus produces a lot of toxins that cause skin barrier breakdown. Therefore colonization with staph aureus could be contributing to skin breakdown and allowing foods to enter through the skin,” explains Dr. Donald Leung, one of the study researchers.
Leung and his colleagues looked at the medical records of 718 children with eczema, aged 0–18, who had been patients at National Jewish Health, and then compared their allergy blood test results, skin-prick test results and food allergy diagnostic codes to the rates of staph infection. In all scenarios, patients whose eczema was colonized with staph aureus were more likely to have allergies – and in particular, peanut allergies – compared to those who didn’t have the staph aureus bacteria.
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For example, 59 percent of patients with staph aureus had strongly positive skin tests for peanut allergy, compared to 47 percent in the patients without staph aureus. When it came to differences in peanut allergy prevalence according to levels of peanut-specific IgE in blood tests, the results were even starker: 57 percent of the patients with staph aureus had levels of peanut-specific IgE that suggest an allergy to the legume, compared to 14 percent in the cohort without staph aureus. The results were not age-specific.
So far, Leung doesn’t recommend any changes for the treatment of kids with staph aureus bacteria. “More research is needed to determine if the occurrence of peanut allergy results from staph aureus colonization. If future research implicates staph aureus as a cause, then eradication of staph aureus could become an approach to preventing peanut allergy,” he says.