Have you ever craved a peanut butter sandwich in school but couldn’t eat any nut products due to the school being nut-free? At this moment you start to think about all the kids in your class that are allergic to peanuts. The number is alarming! I bet you have thought many times about why they are allergic and think that it must be genetic or something. What if I told you that those allergies were not random or due to genetics, but instead they were caused by our approach to medicine and hygiene.
Fig. 1 - Peanut allergies are all too common in schools today. (source: Eliza Marz, “Thriving With Allergies” blog)
Allergies have been on the rise ever since 1997 with their prevalence increasing three-fold between then and 2008 . An allergy is described as an overreaction to a substance that should be harmless . Our immune system, which is our body’s protector from pathogens and foreign substances, gets overstimulated during an allergic reaction, causing inflammation and rashes on a minor scale, and can even close off airways during severe allergic reactions . Food allergies are no joke either. Imagine going to a friend’s house and being scared to eat, or not being able to eat a birthday cake because you cannot read the ingredients. Even worse, imagine being afraid to kiss someone because of what they ate! Food allergies are not fair to those suffering from them, but they are around us at an all-time high. Without a method to treat allergies, medical professionals are trying to understand why food allergies are becoming more prevalent and are striving to come up with preventative methods.
Currently, medical professionals specializing in allergies have turned to the hygiene hypothesis and lack of early exposure as a plausible explanation for this rise. The hygiene hypothesis simply states that the environments in the developing world are becoming too sterile, ultimately resulting in an immature immune system that hasn’t had a chance to “practice” against enough foreign substances . The lack of exposure to these substances, especially foods, are being noted as a driving factor in the increase of food allergies.
What exactly does “lack of exposure” mean and how does this relate to food allergies? Simply, lack of exposure refers to not coming into contact with common allergens as a young child when one’s immune system is developing. For example, if a parent does not feed their child peanuts for the first 2 years of the child’s life, then that child has lack of exposure for peanuts. The Learning Early About Peanut (LEAP) experiment from the Immune Tolerance Network (ITN), studied the early exposure to peanuts in 640 infants from the United Kingdom . In the LEAP study, infants with either eczema or egg allergies were assigned to a treatment group, where they consumed peanuts, or a control group where they avoided peanuts until age 5 . After the study concluded, it was found that only around 1.9% of those who could consume peanuts developed an allergy to them. Conversely, nearly 7 times the number of infants who avoided peanuts until age 5 developed a peanut allergy . This supported the idea that early exposure to peanuts can decrease the risk for food allergies in the future by strengthening the immune system.
Fig. 2 - Feeding peanuts to babies may decrease their risk of future food allergies. (Modified with permission from Petr Kratochvil)
This immune tolerance stems from your gut - specifically the microbes within it. These bacteria can produce metabolites which directly influence the development of immune tolerance to specific proteins . For example, peanuts have specific proteins on their surface which need to be recognized as harmless to the host . If this recognition does not occur, then the individual will have a peanut allergy. You may be asking how this recognition takes place? Exposure! You must be exposed to the peanut to develop tolerance. So, where does the gut come into play? The peanut must be ingested and degraded by the bacteria in your gut. These bacteria then produce the metabolite specific to peanuts, bring it to the immune system, allowing the immune system to develop tolerance .
So, what can you do about this? Spread the new data that supports early exposure. Many individuals may still be grasping onto the notion that early exposure to common food allergens increases allergies. Tell them that this is not supported anymore, link them the LEAP study,* and explain how early exposure can affect immune system development!
Note: While this evidence is quite strong, keep in mind that it is still one study and you should consult your doctor before making any drastic changes to your child’s diet.
 Sicherer SH, Muñoz-Furlong A, Godbold JH, Sampson HA. US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow-up. J Allergy Clin Immunol. 2010; 125(6):1322-1326. doi.org/10.1016/j.jaci.2010.03.029 https://www.jacionline.org/article/S0091-6749(10)00575-0/fulltext
[2)] Galli, S. J., Tsai, M., & Piliponsky, A. M. (2008). The development of allergic inflammation. Nature, 454(7203), 445–454. doi:10.1038/nature07204 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3573758/
 Center for Biologics Evaluation and Research. (2018, March 27). Consumers (Biologics) - Asthma: The Hygiene Hypothesis. Retrieved from https://www.fda.gov/biologicsbloodvaccines/resourcesforyou/consumers/ucm167471.htm
 Du Toit, G., Roberts, G., Sayre, P. H., Bahnson, H. T., Radulovic, S., Santos, A. F., … LEAP Study Team (2015). Randomized trial of peanut consumption in infants at risk for peanut allergy. The New England journal of medicine, 372(9), 803–813. doi:10.1056/NEJMoa1414850 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4416404/
 Pascal, M., Perez-Gordo, M., Caballero, T., Escribese, M. M., Lopez Longo, M. N., Luengo, O., … Mayorga, C. (2018). Microbiome and Allergic Diseases. Frontiers in immunology, 9, 1584. doi:10.3389/fimmu.2018.01584 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056614/
 Mueller, G. A., Maleki, S. J., & Pedersen, L. C. (2014). The molecular basis of peanut allergy. Current allergy and asthma reports, 14(5), 429. doi:10.1007/s11882-014-0429-5 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4785306/
 Kim, C. H. (2018), Immune regulation by microbiome metabolites. Immunology, 154:220-229. doi:10.1111/imm.12930 https://onlinelibrary.wiley.com/doi/full/10.1111/imm.12930
About the Author: Brenton Travers
Brenton Travers is a rising senior at the University of Massachusetts Amherst pursuing a dual degree in Microbiology and Public Health as a member of the Commonwealth Honors College.
As someone who has had severe food allergies for my entire life, a cure or preventative method is always on my mind. I always wonder why I have the allergies I do and how my childhood could have shaped my immune system. The amount of people with allergies have become noticeable over the years and I feel like the alarming number of allergies is not just a coincidence. This was ultimately my purpose of writing this blog; to expose others to allergies and explain that allergies may not be as random as once thought. As a pre-medical student, I plan to go to medical school and specialize in Immunology. My goal is to give back to the community I have been apart of, teach children and their families about allergies, and hopefully make an impact in the allergy field.
More From That’s Life [Science]