Geographic variation may give clues to food allergy

“Geographic variation may provide insights into some of the causes of food allergy in Australia”, states a Canberra based allergy specialist in separate articles published in the December edition of Annals of Allergy Asthma and Immunology and online in the journal Pediatric Allergy and Immunology.

Working with Drs Sunday Clark (University of Pittsburgh), and Carlos Camargo (Harvard Medical School), Dr Raymond Mullins, a Canberra-based allergy specialist, examined nation-wide prescription rates for infant hypoallergenic formulae (given to babies with multiple food allergies), EpiPen devices (used to treat life-threatening allergic reactions) and hospital admissions for serious allergic reactions (anaphylaxis).

They found that hypoallergenic formulae and EpiPens were prescribed much more often to young children in southern compared to northern sunnier regions of Australia. Hospital admissions for anaphylaxis were also more common in southern regions. The authors examined a number of factors to try to explain their findings including regional differences in income, employment, housing density, socioeconomic status, housing or population density, or access to medical care.

“The only thing that fell out was latitude (distance from the equator), and thus indirectly intensity of sun exposure and indirectly, ability of the skin to make vitamin D from sunlight”.

“Our findings likely represent real regional differences in rates of food allergy and anaphylaxis in Australia. Taken together with similar findings in the USA, this raises the possibility that lesser sun exposure and lower vitamin D levels might be one of several factors playing a role in triggering food allergy”.

“Indeed, a similar geographic pattern has been described with other immune system related diseases such as multiple sclerosis and type I diabetes” say Mullins. “We also know that vitamin D influences the developing immune system in many ways and that low levels are seen in many individuals in Australia. And in the last few years, low vitamin D levels have been implicated in increasing the chance of getting hay fever and asthma as well”.

But the authors caution against over interpreting their study. “This is not the answer to the food allergy epidemic we have seen in the last decade. If confirmed to play a role, vitamin D will likely be one of many factors playing a role in food allergy development. And it’s important that people don’t discard the “safe-sun” message that has prevented so many skin cancers in Australia”.

“Allergic disease in general, and food allergy in particular, is a major public health issue in Australia. ‘Generation A’ – the ‘allergy generation’, has already been born. We need to identify causative factors to help with the development of preventive strategies to stem the ongoing increase, and we need to encourage clinical studies to better treat those with already established disease. It’s early days yet, but our results lay an important foundation for further work on vitamin D and allergy.”