The Five "Ds" of food allergy
Australia has the unfortunate title of being the food allergy capital of the world. Recent research, led by Professor Katie Allen, found that one in 10 infants suffers from a food allergy, which is the highest prevalence of food allergy ever reported in the world.
Murdoch Children's researchers are global leaders in research which seeks to uncover the evolution of the food allergy epidemic. Professor Allen leads six allergy studies at the Institute; one of these is the HealthNuts study which involves 5300 infants and is the largest population based study of food allergy ever mounted. It is through this study that researchers have concluded that the rise in allergies is most likely a result of our modern lifestyle. Results from the study have generated five hypotheses relating to increases in the prevalence of food allergy that, Professor Allen says, can be summarised simply as the five ‘D’s’ - diet, dogs, dirt, vitamin D and dry skin.
Diet
For babies
The allergy team found that parents who delay giving their babies allergenic foods could be doing more harm than good, with a 2011 study showing the rate of egg allergy significantly increases among toddlers who are introduced to the food after 12 months of age. The research finding contributed to the changes in the National Infant Feeding Guidelines which now recommend that parents should introduce solids such as eggs around the age of six months, not after 10 months as initially directed. This is supported by new research suggesting the same for peanut.
In pregnancy
There’s no evidence that avoiding potentially allergic foods like nuts in pregnancy lowers the risk of children developing an allergy.
Dogs
A 2012 Institute study found having a dog that lives in the home could reduce the likelihood of allergies in infants. The study was also found that having older siblings reduces a child’s likelihood of developing an allergy. This finding supports the ‘hygiene hypothesis’ which is a theory which states that the immune system needs to be exposed to appropriate stimulation during development so that it is ‘trained’ to attack things that might cause us harm (such as bacterial or viral infections) while ignoring harmless things such as foods. A research trial at the Institute has commenced to test whether the anti-TB vaccine (BCG) can kick start the immune system in a similar way and prevent allergic disease in early life.
Vitamin D
Our researchers found infants who are vitamin D deficient were three times more likely to have an egg allergy and 11 times more likely to have a peanut allergy. Those with vitamin D deficiency were also more likely to have multiple rather than single food allergies, with the odds increasing to 10 times more likely among those with two or more food allergies. Researchers at the Institute are now undertaking a study which aims to find out if vitamin D supplements in the first year of life reduces the risk of food allergy and other early life illnesses such as wheezy bronchiolitis. Since Australia is one of the few Westernised countries that does not fortify the food chain supply with vitamin D, this research will provide world first evidence about the role of the ‘sunshine vitamin’ in early development of the immune system.
Dry skin
Researchers identified an ‘eczema gene’ which increases a persons risk of being sensitive to common allergic foods. Researchers say the findings support the hypothesis that sensitisation to food can occur through the skin and dry skin may increase the risk for infants to become sensitised to common allergenic foods.
Dirt
Another finding that supports the hygiene hypothesis is a study which found that when babies used pacifiers that had been dropped on the ground, their risk of allergy was lower.
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