Interesting causes for peanut allergy identified
The incidence of peanut allergy has continued to rise over the last several decades and now affects approximately 1.5 million people in the U.S. The cause for this epidemic is largely unknown.
Most investigators have assumed that the rising incidence of peanut allergy is related to the environmental factors that are associated with the current allergy epidemic. Additionally, maternal exposure to peanut during pregnancy and during breastfeeding has also been implicated in causing peanut sensitization. However, these views are largely challenged by a recent article.
In this investigation, The Avon Longitudinal study of Parents and Children, 13,971 pre-school children were followed in southwest England since their births between 1991-1992.
Forty-nine children were identified as having a history consistent with peanut allergy and indeed 29 of 36 tested individuals had positive challenges to peanut.
Analysis of these 49 individuals as well as the 23 individuals with bona fide peanut allergy revealed very interesting associated findings.
Notably, cord blood analysis revealed no detectable IgE to peanut indicating in utero exposure was not likely to account for the sensitization. Of further note, maternal dietary factors also had no correlation with peanut allergy. However, there was an association between the duration of breastfeeding and peanut allergy; the significance of this is unclear.
Notably, there was a strong and statistically significant association between consumption of soy milk or soy formula in the first two years of life and the development of peanut allergy.
This consumption typically preceded development of peanut allergy. The association with soy protein exposure and peanut allergy could arise from cross sensitization through common episodes that may prime T cell responses.
Of further interest, rash over the joints and skin creases were significantly associated with peanut allergy. The severity of the rash had a strong positive correlation with the development of peanut allergy.
In contrast, milk allergy was not associated with peanut allergy.
Analysis of detailed interview data revealed that about 90% of individuals with peanut allergy were exposed to skin creams that contained peanut oil especially during the first six months of life.
The uses of these creams occurred largely during the periods when the children were suffering from rashes and also preceded the onset of peanut allergy.
In contrast, the maternal use of breast creams containing peanut oil showed no association with the development of peanut allergy.
In conclusion, sensitization to peanut protein may occur in children through the application of creams with peanut oil to inflamed skin.
This is particularly important since many infant lotions contain peanut oil, which has trace but significant amounts of peanut protein.
Clearly, if these results are reproduced by other investigators then they will provide a rational approach for abating the rising incidence of peanut allergy and possibly other allergic disorders.
Lack G et al. New Engl J Med 2003; 348:977-985
