Medical anthropologist Teresa McKeel has personally experienced the troubles of allergies; her father died from a severe allergic reaction caused by a bee sting. In the process of exploring the mystery of allergies in modern medicine, she has comprehensively examined the phenomenon of allergies, from the dangerous experiments of early immunologists to the challenges currently faced by allergy sufferers, and the latest advances in allergy treatments. She has interviewed immunologists and allergists, and has also sought perspectives from air quality controllers, family members of patients, pharmaceutical companies, research institutions, and government agencies, aiming to provide a comprehensive analysis of the phenomenon of allergies.
Through in-depth exploration, McKeel presents to readers the complexity behind allergies: what allergies are, why people suffer from them, and why the phenomenon of allergies is intensifying. While she cannot reveal all the truths about allergies, her efforts allow us to gain key knowledge to better cope and prepare when facing allergy problems.
On the other hand, Elizabeth is an engineer and a mother whose three children suffer from various forms and degrees of allergies. Her eldest daughter has been troubled by eczema and allergic reactions to multiple foods since infancy, while her son also has eczema and is allergic to peanuts and barley. Elizabeth is concerned about finding more potential allergenic food sources for her children. Her younger daughter was a dairy allergy sufferer and is now just lactose intolerant, which is somewhat easier to manage compared to her other two children.
Elizabeth’s own practices and experiences growing up have given her a deep understanding of allergies. Not only has she become a knowledge disseminator on allergies, but she has also established a support group for parents of children with corn allergies, striving to share her insights with other parents. She speculates that her two children might have altered their gut microbiomes and triggered food allergies as they were hospitalized with high fevers as infants and were given antibiotics. Although she feels guilty about her son and regrets not learning from her daughter’s experiences, believing that early antibiotic exposure may be the root cause of one problem after another, the rarity of allergies in her family makes her more convinced of her guess.
For Elizabeth’s family, the topic of food allergies is a daily occurrence, but for Elizabeth’s parents, the term was once merely science fiction. Although they were initially skeptical, dismissing allergies and the like as unfounded, after witnessing Elizabeth’s children, Viola and Blair, being rushed to the hospital more than once due to allergic reactions to food, they had to accept this harsh reality.
Food allergies have had a profound impact on Elizabeth and her children, and she needs to carefully plan every detail of every meal for the family. Her life seems to revolve around the kitchen and food, starting with careful preparations from early morning, Elizabeth needs to avoid using any ingredients that may trigger an allergic reaction in her children to ensure they can safely enjoy their meals.
Every day, she not only has to prepare the most special lunches for her children’s entire school but also thoughtful snacks to ensure that her children will not come into contact with potential allergens while at school. She handcrafts all these foods because even the packaged foods that are readily available on the market have a high probability of containing some potentially dangerous ingredient, enough to trigger an allergic reaction in one of her children.
Even when traveling, safety concerns have sometimes been the source of their nightmares. A shared vacation experience turned critical when Brian had a severe allergic reaction due to cross-contamination risks in the dorm, leading to an emergency hospital admission. Elizabeth firmly states that they will no longer choose any accommodation that cannot assure hygiene and safety.
Brian, though still young, understands his allergies well. When asked why he can’t eat certain foods, he can clearly answer – “It’s because it causes Brian to have an allergy, it makes me sad. Mom has to give me a shot, and then we go to the hospital.” He has a vivid memory of the EpiPen, the epinephrine auto-injector, and the pain it causes.
As a sensitive mother, seeing her child panic and run away from the EpiPen breaks Elizabeth’s heart. She feels guilty, because not only does the child associate the EpiPen with pain, but she also thinks she might be responsible to some extent for her child’s allergies.
In fact, Elizabeth’s guilt is not uncommon. Many parents of children with allergies are exploring what could have triggered such conditions in their children. They scrutinize their lifestyle, family environment, and habits, worried about what factors may have laid the groundwork for their children’s suffering. Particularly for parents whose children suffer from both severe eczema and food allergies, they continually trace back every little detail of the past, hoping to find decisive clues and give special significance to those seemingly minor daily details.
We understand that the impulse to find the cause is itself filled with rationality. Whether it’s mothers like Elizabeth or many others I have interviewed about the origins of allergies, they all have their theories, and most of them align with the cutting-edge views of the scientific community – environmental changes may be the culprit.
In the past two centuries, our society’s culture and daily habits have been under careful observation, our commitment to parsing the potential role they play in escalating anxiety. We have good reason to blame ourselves to some extent. The overall pattern of modern lifestyles is likely the deeper cause behind the recent increase in allergy symptoms.
To deeply understand how modern life triggers some of the main issues related to allergies, especially those related to food production, dietary habits, antibiotic use, and birth practices, you might find yourself sitting across from a slender, clever, and empathetic blonde woman – to her students, she is Dr. Nagler, and to her friends and colleagues, she is Kathy. In every conversation about allergy experts, Nagler’s name seems to come up in connection with food allergy issues. This is not surprising, as she is recognized as one of the world’s top immunologists.
Dr. Nagler’s research focuses on the impact of the gut microbiome on the development of food allergies in children. She has dedicated decades to this area and remembers the increase in food allergy rates in the late 1980s. “I’ve witnessed this shift myself,” she said, as she turned her computer screen to show me the relevant statistical charts. On a clear spring afternoon, we sat in her office at the University of Chicago. She added, “I have two children, one 23 and the other 27, so I’ve been watching this closely. It was during their school years that the campus banned cupcakes. It was then, from the late ’80s to the early ’90s, that the incidence of food allergies began to rise significantly. Back then, the American Academy of Pediatrics erroneously advised pregnant women, nursing mothers, and children under four with potential allergies to avoid peanuts and other potential allergens. This approach did not solve the problem; instead, it aggravated the situation, accelerating the increase in allergy symptoms. Now, all work is focused on how to intervene with food exposure at an early age.”
Dr. Nagler’s words are not in vain. Indeed, there is a now widely known early peanut allergy study—LEAP Study—led by Dr. Gideon Lack of King’s College London’s multinational research team, and published in The New England Journal of Medicine in 2015. This study found that for years, parents have been misled not to feed their children under the age of 3 with peanut-containing foods, which has actually led to a significant increase in the incidence and severity of peanut allergies. The infants participating in the study (aged 4 to 11 months) were divided into two groups, one with parents continuing to follow the advice to avoid feeding peanuts, and the other being told to start exposing their children to peanuts. Both groups of infants underwent peanut sensitivity skin prick tests. The study found that, in children with negative peanut sensitivity tests, the peanut allergy rate was 13.7% in the peanut avoidance group at the age of 60 months, whereas it was only 1.9% in the peanut-exposed group. Among the children with positive peanut sensitivity tests, the peanut avoidance group had an allergy rate as high as 35.3%, while the allergy rate in the peanut-exposed group was significantly reduced to 10.6%.
Latest research results from Melbourne, Australia, revealed encouraging news: following the significant effects of the LEAP study, the guidelines on peanut intake changed in 2016, and this change has been accompanied by a significant outcome—a 16% reduction in the number of infants with peanut allergies. This finding further confirms the significant protective effect of incorporating peanuts into an infant’s diet.
Despite this, hesitation and concern about introducing potential allergens into a child’s early diet still exist in people’s minds. Just a few years ago, that advice might have been completely the opposite, which inevitably makes parents skeptical about today’s recommendations. It is worth noting that not all experts agree that early introduction of allergens is without fault. For example, Dr. Nagler pointed out that children may already be sensitive to certain substances before they try solid food. Infants may exhibit allergic reactions shortly after birth, which could be related to breastfeeding or skin contact. Therefore, while there might be risks associated with early exposure to allergens, we now understand that outright avoidance is not the solution.
Dr. Nagler has expressed more concern about the formation of early sensitivity in the immune system. She considers how the human body recognizes and gradually develops tolerance to specific foods, while beginning to show sensitivity or adverse reactions to other foods. She also believes that the rise in food allergies is one of the results of transgenerational changes. She observed individuals who previously thought there was no such family history, whose allergy symptoms might occur at any time, commonly in children aged 2 to 5, and now, food allergies in adults are also on the rise.
Dr. Nagler believes that modern industrial lifestyles have triggered changes in our microbiota—the beneficial bacteria that exist within and around our bodies. She has linked chronic non-communicable diseases like inflammatory bowel disease, allergies, obesity, and autism to changes in the microbiome. Alterations in the composition of the gut microbiome—the sum of all microorganisms in our guts, including bacteria and viruses that help us process food—is influencing changes in our immune function.
Recent studies have emphasized the role of dietary habits, antibiotic use, and gut bacteria in the development of allergic diseases. A 2019 study found that the guts of healthy babies contained a specific class of bacteria that provide protection against allergies, which were absent in babies with milk allergies. Research from Brigham and Women’s Hospital also discovered that certain strains of bacteria in the infant gut appear to offer protection against food allergies. Chief researcher Dr. Lynn Bry suggested that our lifestyles have “reset” our immune systems. Further studies indicate that a high cheese intake in the diet could inadvertently exacerbate allergy symptoms, as bacteria in certain cheeses can produce histamine, a natural compound that can provoke an effective immune response.
A study by researchers from the University of California, San Francisco, uncovered a link between three gut bacteria and the production of a lipid molecule called 12,13–diHOME. This lipid molecule plays a key role in reducing the number of regulatory T cells (crucial for suppressing inflammation) in the gut. Concerningly, infants with higher levels of these bacteria have a higher likelihood of developing allergies and asthma in the future compared to other infants.
In contemporary society, due to changes in lifestyle, the composition of people’s microbiota has undergone a significant shift. Diet has played a key role in this. As people shift from eating fiber-rich natural foods to high-sugar, high-fat, highly processed foods, the nutrient sources for probiotics in the gut are limited, subsequently affecting their survival. As researcher Nagler pointed out, the co-evolution of humans and microbes has been disrupted, with the lack of proper food causing the probiotics in our body to be unable to survive.
Nagler emphasized that all organisms, including invertebrates, have a set of associated microbiota that undertake important physiological functions. Without microbiota, life cannot continue. In the human gut, symbiotic microbes numbering up to 100 trillion are processed each year, along with more than 30 kilograms of food protein. As such, cells in the gut barrier need to differentiate between harmful pathogens and harmless antigens.
In a study conducted jointly by Nagler and her former student, immunologist Dr. Onyinye I. Iweala of the University of North Carolina School of Medicine, it was stated that “a functional epithelial barrier intimately interacting with innate immune cells and the microbiota is essential for establishing and maintaining oral tolerance.” This means that maintaining a healthy immune response requires a balance between epithelial cells, the probiotic populations in the gut, and the types of food we consume. Any alteration in this balance could lead to problems like those mentioned earlier for children like Elizabeth.
From Nagler’s perspective, the theory that antibiotics cause food allergies in children is not unfounded. Studies show that as children grow, changes in the gut microbiome increase, and with them the risk of allergic reactions. The role of the early growth environment is particularly critical during a child’s development. Research by Rutgers University and the Mayo Clinic found that children under the age of two who used antibiotics had a higher risk of developing asthma, respiratory allergies, eczema, celiac disease, obesity, and ADHD. This study, which covered 14,572 children born in Olmsted County, Minnesota from 2003-2011, further revealed the risks of early medication use. It was found that over 70% of children had taken antibiotics at least once for respiratory or ear infections within the first 48 months of life. Additionally, recent studies have found that the use of antibiotics can promote the growth of non-pathogenic fungi in the human gut, which may in turn exacerbate the severity of respiratory allergies.
Recent studies indicate that cesarean delivery and the use of antibiotics are closely linked to changes in the gut microbiome of infants and an increased risk of allergies. Research experts point out that during natural childbirth, infants are exposed to the mother’s probiotics, laying the foundation for the normal development of their gut microbiome. This exposure is very natural during vaginal delivery, and subsequently, through breastfeeding, more probiotics are introduced into the infant’s gut, providing protection for their healthy growth.
Even simple everyday activities, such as changing bed sheets, can have an impact on our microbial environment. Researchers from the Department of Biology at the University of Copenhagen and the Danish Pediatric Asthma Center have revealed through analysis of bed samples from 577 infants and respiratory tract secretions from 542 infants, the presence of up to 930 different types of bacteria and fungi. They pointed out that there is a certain correlation between microbes in bed dust and the microorganisms inside children, and these bacteria seem to interact and affect the child’s health.
The study also suggests that increasing the frequency of changing bed sheets might benefit the health of the nasal and airway microbiome. The presence of a more diverse range of bacteria in the environment helps strengthen the function of our immune system. In other words, the microbial diversity in natural environments is beneficial to our overall health.
In exploring allergy issues caused by modern lifestyles and daily habits, the feelings of parents should not be overlooked. Taking the case of Elizabeth as an example, she felt that she might have indirectly caused her child’s severe food allergy, reflecting the heavy responsibility parents feel for their children’s health. Elizabeth’s decision to treat her child with antibiotics in an emergency was correct at the time, but years later, it still left her feeling guilty, an emotion resonating with many parents caring for children with allergies.
Parents have to make the best possible choices for their children at every step of their growth and often feel anxious about it. This unease usually starts during pregnancy when parents need to think about how to prevent adverse reactions like allergies.
In an age of information overload, parents face the challenge of making wise choices among many contradictory pieces of advice. Whether it’s reputable medical websites or unreliable online videos, there is an abundance of suggestions. We should understand that despite the multitude of information sources and their complexity, parents should make the most appropriate decisions for their children based on the best available evidence and their own circumstances.
Valuing the finest medical advice can bring us great benefits. Immunology experts, with their profound knowledge, foresee the complex interactions between the immune system and the rapidly changing environment. This is a reminder for those struggling with allergic diseases and their family members to grant themselves proper rest. We need not blame ourselves for why we have allergic reactions; the actual situation is much more complex than we imagine.
Cherish your health, listen to the signals of your body, and make wise choices. Care for yourself and also for those around you who are fighting the battle with allergic diseases. Living in a constantly changing world, understanding and adapting to the complex biological environment around us is each person’s responsibility, and it is also our collective challenge.
