There’s a lot of confusion and speculation about what causes food allergies. A recent post here on PeanutAllergyFacts.org tackled this issue, in fact, as part of an overall look at why there’s been a rise in food allergies. A recent report released by the National Academies of Science called Finding a Path to Safety in Food Allergy Assessment of the Global Burden, Causes, Prevention, Management, and Public Policy challenges what we think we know about food allergies. With regard to why food allergies develop, report authors say that the contributing factors contributing are poorly understood. The report lists the most common hypotheses for why individuals develop food allergies are as follows: (1) microbial hypothesis; (2) allergen avoidance hypothesis; (3) dual allergen exposure hypothesis; (4) nutritional immunomodulation hypothesis; and (5) other hypotheses.
Here’s a very brief introduction to each hypothesis:
1. Microbial hypothesis – Incorporates the “hygiene hypothesis” and the “old friends hypothesis”, which suggest that a host of environmental factors impact our microbiome (all of the microbes that live on and in our bodies) and those microbes interact with our immune system in positive (or negative) ways. Changes in the microbiome may contribute to the development of food allergies.
2. Allergen avoidance hypothesis – Suggests that the avoidance of potential allergens in the prenatal and early infant periods could prevent allergies. Because the evidence does not support avoidance as a means to prevent food allergy, this is no longer recommended.
3.Dual allergen exposure hypothesis – Proposes that allergic sensitization to foods may occur through skin exposure to allergenic proteins, especially when the skin is broken (as in eczema). Further, the hypothesis states that when proteins are introduced orally, by eating potentially allergenic foods, before this sensitization occurs through the skin, allergy is avoided and long-term tolerance happens. This has now been proven for peanuts in the LEAP Study.
4. Nutritional immunomodulation hypothesis – This hypothesis suggests that not only food allergens, but also other constituents that influence the immune system play a part in the development of food allergies. For instance, vitamin D, fatty acids, and folate may all pay a part in the development of food allergy.
5. Other Hypotheses – Ongoing research is considering the role of obesity and diabetes in the development of food allergies because they have also been on the rise at the same time as food allergies. Likewise, there are some who suggest that increased consumption of processed foods or food additives, genetically modified foods, and eating more fast food cause food allergies. However, no studies have proven a cause and effect relationship in any of these areas of study.
Other unproven contributors to food allergy include vaccinations. Peanut oil is not an ingredient in any US licensed vaccine listed by the Centers for the Disease Control and Prevention (CDC). There is no research that supports a causative relationship between vaccinations and peanut allergies. In fact, Children’s Hospital of Philadelphia (CHOP) specifically states on their Vaccination Education Center website that peanut oil, as some people suggest, is not used as a part of vaccinations. The CDC provide excellent information on vaccines at their website, especially regarding their benefits, ingredients, and safety.
Finally, it is important to note that genetics also likely plays a part in food allergy development. Whether a stand-alone predisposition toward allergy or a matter of gene expression being influenced by environmental factors, researchers continue to try to understand how individuals’ genes influence food allergies. There are many unknowns about how and why food allergies develop. Researchers cannot answer that question definitively.
But that doesn’t mean we should do nothing. In fact, the new recommendations for early introduction of peanut foods to prevent peanut allergies is an exciting development based on rigorous research. To quote Matt Greenhawt, MPH, MD, pediatric allergist and researcher from Colorado Children’s Hospital, in a recent interview “We know that these children with severe eczema and or egg allergy had about an 80 percent reduced chance of developing peanut allergy if peanut was introduced between four to 11 months of life.That’s a whole generation of children who never have to develop this allergy.”