How the Microbiome May Solve the Mystery of Peanut Allergies

Post by abrookhart

Most people see peanuts as a delicious snack, but for those with an allergy, peanuts can be deadly. An allergic reaction can begin mere seconds after exposure, causing symptoms like vomiting, abdominal pain, coughing, wheezing, and anaphylaxis, the latter of which can be fatal [1, 2]. Almost half of all people with food allergies will visit the emergency room at some point in their lives due to an allergy-related incident [3]. Beyond the trauma of suffering from a life-threatening reaction, allergies can affect people’s quality of life, cause daily stress, and even impact their social life. But new research is pointing to bacteria for promising solutions.

Roughly 4.6 million adults in the United States have a peanut allergy [4]. This number is only increasing over time. Food allergies were almost unheard-of decades ago, but today, it is difficult to find an allergy-free elementary school. Currently, peanut allergies affect about 2.5% of children, meaning that one in forty kids have a peanut allergy [5]. Despite how prevalent peanut allergies are, they are still a mystery. The cause of allergies is not yet fully understood, nor is the reason why allergies are becoming more common. Genetics appear to be a contributing factor, but environmental factors, such as diet, are believed to be involved in causing peanut allergies as well [6, 7].

Figure 1. A positive skin test for peanut allergy. A medical professional makes small needle pricks in the skin, then adds allergens like peanuts to see if a reaction occurs. Photo credit: Kornoeljielife via Flickr.

Allergies are caused by the immune system mistaking a harmless piece of food for a pathogen. People with a peanut allergy produce antibodies that bind to proteins from peanuts, resulting in a major immune response [2]. Essentially, the immune system overreacts to something that is not harmful, like a peanut.

How can we change this immune system reaction to prevent or cure peanut allergies? The microbiome may provide some answers. The microbiome is a new area of study focused on the collection of microorganisms found all over the human body. These microorganisms play an important role in keeping the immune system in check. Various studies have shown that children with peanut allergies and other food allergies have a less diverse microbiome than healthy kids [8–10]. In fact, these changes to the microbiome may begin at a young age, and could even be driving allergy development [11].

The bacteria in your microbiome regulate your immune system by breaking down the food you eat and producing short-chain fatty acids (SCFAs) in the process. These SCFAs are involved in many immune system-related tasks, such as preventing tumors and reducing inflammation [12]. So, SCFAs are important for the immune system to function properly, and a lack of SCFAs may cause immune dysfunction in children with allergies.

In addition to having a less diverse oral microbiome, children with peanut allergies were found to have lower levels of SCFAs and higher levels of interleukin-4, a key immune system compound involved in allergic reactions [8]. Interleukin-4 is produced during an allergic reaction, and it triggers production of the main antibody involved in the allergic response, IgE, which is the physiological basis of a peanut allergy [13]. So, interleukin-4 is central to peanut allergies, and a healthy microbiome seems to be key to regulating interleukin-4 levels. This finding suggests that changes to the microbiome may alter the way the immune system functions, leading to peanut allergies.

Figure 2. Allergy shots are sometimes given to people in an effort to reduce their symptoms. This is a form of immunotherapy that may help the body become accustomed to the allergen. Photo credit: Neeta Lind via Flickr.

Although research into the connection between the microbiome and peanut allergies is ongoing, this work could one day help us cure peanut allergies. A treatment being investigated is probiotics, which contain live bacteria and may increase microbiome diversity, One study found that probiotics could decrease IgE and interleukin-4 levels in mice [14]. In another study, researchers gave children with peanut allergies a probiotic and oral immunotherapy. They found that 90% of children who were given this combination treatment became desensitized to peanuts, compared to 7% of untreated children [15].

It may be a while before a microbiome-based allergy cure hits the shelves. But in the meantime, there are steps we can take to keep our microbiome diverse, such as eating a healthy, fiber-rich diet and minimizing antibiotic use when possible. Understanding the microbiome’s role in causing peanut allergies will bring us one step closer to preventing and treating peanut allergies. There is hope that a treatment is coming for people with peanut allergies.

Works Cited

[1] A. W. Burks, “Peanut allergy,” The Lancet, vol. 371, no. 9623, pp. 1538–1546, May 2008, doi: 10.1016/S0140-6736(08)60659-5.

[2] M. Pansare and D. Kamat, “Peanut Allergies in Children—A Review,” Clin Pediatr (Phila), vol. 48, no. 7, pp. 709–714, Sep. 2009, doi: 10.1177/0009922808330782.

[3] R. S. Chinthrajah et al., “Oral immunotherapy for peanut allergy: The pro argument,” World Allergy Organization Journal, vol. 13, no. 8, p. 100455, Aug. 2020, doi: 10.1016/j.waojou.2020.100455.

[4] C. Warren, D. Lei, S. Sicherer, R. Schleimer, and R. Gupta, “Prevalence and characteristics of peanut allergy in US adults,” Journal of Allergy and Clinical Immunology, vol. 147, no. 6, pp. 2263-2270.e5, Jun. 2021, doi: 10.1016/j.jaci.2020.11.046.

[5] H. E. Cannon, “The economic impact of peanut allergies,” Am J Manag Care, vol. 24, no. 19 Suppl, pp. S428–S433, Oct. 2018.

[6] X. Hong et al., “Genome-wide association study identifies peanut allergy-specific loci and evidence of epigenetic mediation in US children,” Nat Commun, vol. 6, no. 1, p. 6304, Feb. 2015, doi: 10.1038/ncomms7304.

[7] L. Gideon, F. Deborah, N. Kate, and G. Jean, “Factors Associated with the Development of Peanut Allergy in Childhood,” The New England Journal of Medicine, p. 9, 2003.

[8] H. Ho, Y. Chun, S. Jeong, O. Jumreornvong, S. H. Sicherer, and S. Bunyavanich, “Multidimensional study of the oral microbiome, metabolite, and immunologic environment in peanut allergy,” Journal of Allergy and Clinical Immunology, vol. 148, no. 2, pp. 627-632.e3, Aug. 2021, doi: 10.1016/j.jaci.2021.03.028.

[9] S. Bunyavanich et al., “Early-life gut microbiome composition and milk allergy resolution,” Journal of Allergy and Clinical Immunology, vol. 138, no. 4, pp. 1122–1130, Oct. 2016, doi: 10.1016/j.jaci.2016.03.041.

[10] M. Fazlollahi et al., “Early-life gut microbiome and egg allergy,” Allergy, vol. 73, no. 7, pp. 1515–1524, 2018, doi: 10.1111/all.13389.

[11] J. H. Savage et al., “A prospective microbiome-wide association study of food sensitization and food allergy in early childhood,” Allergy, vol. 73, no. 1, pp. 145–152, 2018, doi: 10.1111/all.13232.

[12] Y. Yao, X. Cai, W. Fei, Y. Ye, M. Zhao, and C. Zheng, “The role of short-chain fatty acids in immunity, inflammation and metabolism,” Critical Reviews in Food Science and Nutrition, vol. 0, no. 0, pp. 1–12, Dec. 2020, doi: 10.1080/10408398.2020.1854675.

[13] S. Tangye, “Cytokine-Mediated Regulation of Plasma Cell Generation: IL-21 Takes Center Stage,” Frontiers in Immunology, vol. 5, p. 65, 2014, doi: 10.3389/fimmu.2014.00065.

[14] M. Meijerink et al., “Immunomodulatory effects of potential probiotics in a mouse peanut sensitization model,” FEMS Immunology & Medical Microbiology, vol. 65, no. 3, pp. 488–496, Aug. 2012, doi: 10.1111/j.1574-695X.2012.00981.x.

[15] M. L. K. Tang et al., “Administration of a probiotic with peanut oral immunotherapy: A randomized trial,” Journal of Allergy and Clinical Immunology, vol. 135, no. 3, pp. 737-744.e8, Mar. 2015, doi: 10.1016/j.jaci.2014.11.034.

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