A recent review by Melbourne immunology researchers Professor Katie Allen and Dr Jennifer Koplin provides an outline of the current theories for why childhood food allergies are on the increase and therefore the areas which may be targeted through clinical recommendations in an attempt to prevent food allergy.
The theories are grouped and referred to as “the 5 Ds”: dry skin; diet; dogs; dribble (shared microbial exposure); and vitamin D.
Research has shown that babies with eczema have a higher risk of food allergy. Prevention strategies that could be recommended to families as a way to prevent eczema are currently being explored, including avoiding soaps and detergents that dry out the skin and using hypo-allergenic moisturisers to help prevent the breakdown of the skin’s protective barrier.
With regard to diet, current infant feeding recommendations are that solids should be introduced to an infant’s diet around the age of four to six months, irrespective of family history of allergy. Previous advice for feeding babies was to delay giving potentially allergenic foods, like egg and peanut butter, but some studies have suggested that earlier exposure may be protective against food allergy. Current recommendations are that allergenic solids do not need to be excluded from an infant’s solids diet – or from that of mothers who are pregnant or lactating.
Due to concerted efforts to prevent sun-damaged skin and melanoma, many Australians have low vitamin D levels. Mothers who are low in vitamin D are more likely to have babies who are low in the vitamin. Research has shown that babies with low levels of vitamin D at 12 months were three times more likely to have food allergy than those with normal vitamin D levels.
Pet ownership and exposure to microbial diversity are other factors that appear to be linked to a lower risk of developing food allergy. Some consider the high rate of antibiotic use has changed the microbial environment in which we live and that this has had an impact on the prevalence of childhood food allergy.
The review authors advise that investigation of the role of microbiota and vitamin D is ongoing and cannot yet be translated into clinical recommendations.
Reference: Allen & Koplin. 2016. Journal of Allergy and Clinical Immunology. In Practice. pii: S2213-2198(15)00574-7. doi: 10.1016/j.jaip.2015.10.010.