Well, the truth is, no one really knows but there are plenty of theories. In Australia, it is estimated 10% of children under one year old and 4-8% of children under the age of five have a diagnosed food allergy. These are statistics from 2011, so there is a good chance those numbers are higher now.

Remember when you were at school? There may have been one or two people who had an allergy. There probably wasn't a restriction on nuts and you certainly wouldn't have seen any child sporting a headband or badge with an allergy warning.

Allergies were rare 20 years ago. Today, that's simply not the case.

The theories for the increased prevalence of food allergies range from advancements in hygiene, gut health and a lack of nutrients to pollution and reduced exposure of foods. Here we take a look at some of the reasons that may answer the question 'why are food allergies on the rise?'

Changes in our diet

The modern, Western diet is vastly different from traditional dietary practices. We eat more processed and synthetic foods. We're consuming more sugar and unhealthy fats and less fresh fruit and vegetables. We're also consuming genetically modified foods and produce laden with pesticides and herbicides. The limited fruit and vegetables we do eat are farmed in nutrient-poor soil. In some instances, we're eating animals that are fed on a modern diet and given drugs.

This modern-day picture has resulted in changes in our nutrient intake including vitamins and antioxidants. But one of the most significant changes relevant to allergies is our reduction in omega-3 fatty acids and our increase in saturated fats and omega-6 fatty acids which are highly inflammatory.

There is also a suggestion the increased consumption of sugar adds to the level of inflammation and leads to a less favourable microbiome. This is because pathogenic bacteria feed off sugar and as a result, the balance between the "good" and "bad" bacteria is disrupted.

The 'hygiene hypothesis'

One of the most popular theory to the question 'why are food allergies on the rise' is what is known as the 'hygiene hypothesis'. Advancements in medical practices and disease prevention have ensured we live for longer with an improved quality of life. We've seen better sanitation, a wider range of antibiotics and vaccinations that have (regardless of which side of the fence you sit) saved thousands of lives.

However, this theory suggests our germ-free obsession is linked to a declining exposure to microbes and bacteria that may increase the risk of an allergic immune response. Early exposure to bacteria, microbes, viruses, parasites and allergens challenges and helps to build up our immune system. Over time, we tolerate these allergens and the response is less dramatic. This may be why children who grow up with pets have less incidence of allergies.

Our overuse of sanitisation and our under exposure to germs in the natural environment has prevented children from strengthening their immune systems. Instead of running with wet wipes and hand sanitiser, we should be allowing our children to get in the dirt, be licked by a dog (obviously supervised) and be in contact with other 'germy' kids!

Weaning practices

Weaning practices may also be a contributing factor in the rise of food allergies in children. Limited to no exposure to certain food during the weaning period could cause these foods to become allergens when consumed later.

There was a time when health professionals were advising parents to wait until 2 or even 3 before introducing the most allergenic foods such as peanuts, cows milk and eggs. New research advises infants should be fed allergenic solid foods in their first year of life, even those babies who at high risk of an allergy. The World Health Organization recommends introductory of solids should begin no earlier than 6 months of age.

A lack of vitamin D

The 'vitamin D hypothesis' has also emerged given important of the nutrient for the developing immune system and its link with the gut microbiome. As vitamin D is only present in small quantities of food, our main source of the nutrient is from sunlight exposure. Our modern lifestyle of working and living indoors and increased time spent in front of screens limits our opportunity to meet our daily needs. This, coupled with our concern over our time in the sunshine (especially kids), reduces the synthesis of vitamin D in the skin. As a result, vitamin D deficiency is relatively common in Australia including in many pregnant women and newborns.

Exposure to pollutants

Exposure to pollutants is a growing concern for allergies and our broader health status. Specific to allergies, probably the most extensively studied toxic exposure in early life is cigarette smoke. Studies reveal babies who have been exposed to the pollutant before birth or during their first few months born are at an increased risk of developing asthma and allergy later in childhood. There is also growing research into the link between environmental pollutants such as exhaust fumes and chemicals like phthalate esters and allergies.

Rising rates of stress

Stress is one we don't often think about when talking about allergies. However, there have been questions raised about the implications of stress and immunity in relation to the rise in allergies. We do know that for someone with an existing allergy, stress can be considered a trigger for an allergic response. The question is now being asked, could stress be the causative factor in developing the allergy?

Increased maternal allergy

Another theory to answer the question 'Why are food allergies on the rise in children?' is the increase in maternal allergy rates. Studies have found, children born to mothers with an allergy have an increased risk of developing an allergy themselves suggesting a genetic link.

Reduced bacterial diversity

Many researchers are starting to question the significance of the gut microbiome in regard to allergies. This links to both the 'hygiene hypothesis' and our change in diet but also how bacteria is transferred from mother to baby. And with about 80% of our immune system located in the gut, it makes sense a reduced bacterial diversity could play a role in the prevalence of allergies in general.

Caesarean section delivery is more common today than ever before. These children display a very different composition of gut flora than those born vaginally. And there is growing research highlighting the increased rates of asthma in children who were born by cesarean section.

There is ongoing research into the benefits of giving probiotics to mothers early in their pregnancy to help reduce the risk of children developing allergies later in their life.

Other theories for the rise in allergies including more frequent use of medications and antibiotics as well as epigenetic effects. More research is required to better understand most of these theories and what we can do to prevent allergies occurring in the first place.

References

Allergy & Anaphylaxis Australia. (2017). Food Allergy. Retrieved February 3, 2019, from https://allergyfacts.org.au/allergy-anaphylaxis/food-allergy, Kalberg, M. (2018). A new focus on the allergy epidemic - Linköping University. Retrieved February 3, 2019, from https://liu.se/en/article/allergiepidemins-gata-i-nytt-ljus

Prescott, S. L. (2011). The Allergy Epidemic “A Mystery of Modern Life.” The Univesity of Western Australia.<br>Takano, H., & Inoue, K.-I. (2017). Environmental pollution and allergies. Journal of Toxicologic Pathology, 30(3), 193–199. https://doi.org/10.1293/tox.2017-0028

WHO. (2018). WHO | Complementary feeding. WHO. Retrieved from https://www.who.int/nutrition/topics/complementary_feeding/en

Zopf, Y., Baenkler, H.-W., Silbermann, A., Hahn, E. G., & Raithel, M. (2009). The differential diagnosis of food intolerance. Deutsches Arzteblatt International, 106(21), 359–69; quiz 369–70; 4 p following 370. https://doi.org/10.3238/arztebl.2009.0359