It is estimated, based upon this research, that approximately 1 in 10 infants experience a food allergy. We also know that there has been between two to threefold increase in the presentations to emergency departments in Australia because of anaphylaxis (severe allergic reactions) to foods and medications over the past two decades.
In Australia, infants who are particularly at risk of developing a food allergy include those with allergic (or atopic) eczema, particularly where it is moderate or severe in severity, those with a family history of allergies, and infants who are first born Australians whose parents have emigrated from Asia to Australia (more on that later).
People often wonder if allergies are really increasing, or whether they are just being diagnosed more frequently. But good epidemiological evidence from not just Australia, but around the world, does definitely suggest that there has been a true increase in food allergy, allergic eczema and allergic rhinitis (more commonly know as hayfever).
Most of these food allergies are the result of the immune system producing an allergy antibody (called IgE) against proteins contained within foods. The most common foods that cause allergic reactions in children and adults in Australia are cow’s milk, egg, peanut, other nuts (tree nuts including cashew, pistachio, walnut), seafood (crustaceans and fish), wheat and soy. Although many children will outgrow their allergies to egg, milk, soy and wheat, in general allergies to nuts and seafood tend to persist into adult life.
Likewise, allergies that cause hayfever are also caused by the immune system producing allergy antibodies against common environmental proteins. In Australia some of the most common triggers for hayfever are house dust mite (actually the droppings of the mite — yuck!), pollens from grasses, weeds and trees and from the dander (and saliva) from domestic animals such as cats, dogs, rabbits and guinea pigs.
So what has caused the increase in allergies?
This is the $6 million (indexed to trillion) question, which remains largely unanswered. But we do have some tantalising clues and theories about the sorts of things which might be driving the increase in allergies.
We do now have good evidence that for some foods, like peanut and egg, being able to introduce the foods into the diet within the first year of life decreases the risk of infants at risk of food allergy from subsequently developing allergy to these specific foods.
Decades of misguided advice to avoid introduction of peanut and eggs (and other allergenic foods) into the diets of infants in countries like Australia, US and the UK may have indeed contributed to the high levels that we currently see — but it is unlikely to completely explain the rise.
Source: ABC Science