Why Do So Few Of Our Grandparents Have Food Allergies, While So Many Of Our Children Do?

The prevalence of food allergies has dramatically increased in recent decades.

Plenty of theories have been suggested as to why allergies are on the rise in recent times, from an increase in hygiene to changes in diet to spending more time indoors. Yet these theories don’t adequately explain all the aspects seen in the data.

The short answer: no one really knows.

Curiously, this increasing trend in the number of children developing allergies is one that is particularly prevalent in westernized countries, such as the UK, United States, and Australia. Research has shown that when children of an African or East Asian decent are raised in these Western nations, their risk of developing an allergy quickly rises to match those of resident Caucasian children.

This suggests that there are some environmental or cultural factors in these places that are behind the observed increases in allergies. But it also raises the interesting question that as developing nations grow, and populations adopt a more westernized lifestyle, will the levels of childhood allergies rise too? If that is the case, then healthcare costs will also increase.

One of the most common reasons given for the increase in allergies in the Western world is what is known as the hygiene hypothesis. A lot of people think that our obsession with cleaning and ever-increasing hygiene standards – particularly when it comes to children and food – means that we are not exposed to as many allergens or microorganisms as we used to be.

Have Western nations lost touch with the natural bacteria in the environment? Songquan Deng/Shutterstock

It is argued that because the immune system has in effect been shielded from common allergens as a child grows up, when they then experience these triggers later in life, their immune system simply over-reacts and an allergy is formed. Many suggest that this is exacerbated by over-cleanliness in our homes. It might also be related to the fact that, in general, we are spending less and less time outside.

This dove tails into another theory proposed by Professor Graham Rook, which suggests that over the last century or so we have lost touch with a lot of the “good” bacteria once found all over our skin, in our guts, and probably lining our throats.  

Professor Rook calls this the “old friends” mechanism, and it's related to the hygiene hypothesis. The "old friends" mechanism argues that it's not the increase in cleanliness that is driving allergies. In fact, our increase in hygiene has done more good than harm considering its critical role in preventing the spread of disease-causing pathogens. Instead, it is our lifestyle that has changed, and this as a result has caused a disconnect between us and these old bacterial friends.

The shift from being outside to inside is notable because the bacteria we as children are now exposed to has radically altered. There is no doubt that kids are exposed to fewer bacteria, in both number and diversity, and this could in part be behind the creeping number of reported allergies.

Spending less and less time outside and away from animals in Western nations could be contributing to the rise of allergies. October:Sonata/Shutterstock

This is not a radically new idea, as it has previously been noted that children growing up on farms are far less susceptible to allergies. For example, those who grow up on farms around animals are half as likely to develop hay fever, while exposure to dogs can cut the risk of getting asthma by up to 13 percent.

But researchers are also looking into another potential driver behind the ever-growing number of children developing allergies: diet. Could the changes in what people in the Western world have been eating over the last half-century contribute to more allergies? Some certainly think so.

As strongly as one camp says that exposing children at an early age to certain common allergens, such as eggs and peanuts, will reduce the likelihood that they will then go on to develop an allergy to that food, the other camp says that children should be avoiding it.

Strangely, there may even be a link between a child’s diet and their risk of developing hay fever, which is not usually thought to be related to food. A study asking over 4,000 parents about their children’s diet and their resulting allergies found that children fed fish at least once a month when they were one year of age were up to 30 percent less likely to develop an allergic reaction to pollen.

This is not the first time that fish has been found to have an effect on the allergy rate in kids, and some suggest that it could be down to the high levels of omega-3 fatty acids in the food. It has been argued that this molecule has an anti-inflammatory effect, while the oils found in vegetable oils – which are becoming more prevalent in Western diets – have the opposite effect.

It might not only be the child’s diet, however, that can have an impact on their chances of developing an allergy. What the mother eats while pregnant and breastfeeding could be significant too. Interestingly, new research has found that women who took fish oil supplements while pregnant had kids who were 30 percent less likely to have an egg allergy, while those who regularly took probiotics had children 22 percent less likely to develop eczema.

There is some evidence to suggest that the oils found in fish might help reduce the risk of developing allergies. Lapina/Shutterstock

Some recommend that pregnant and breastfeeding women avoid foods such as peanuts, dairy, and eggs, with the logic that the proteins can pass to the baby. But the same study that found fish oil supplements were a benefit, also reported no evidence that any other aspects of a mother's diet had an impact.

As you have probably figured out by now, the whole field of allergies – be it food, asthma, or hay fever – and their rise in modern times is a convoluted one. Just as there is no single gene for height and no simple cure for cancer, there is likely no silver bullet for allergies. The best rule to follow is what we should all being doing anyway, and that is if you are in any way concerned, listen to what your doctor has to say about your own situation. VIA: http://www.iflscience.com