The 'democratization' of allergies: an environmental and social breeding ground spurs the rise of cases and new allergens

The immune system is the best of the defensive armies: it constantly protects the body from any external threat and almost always wins. Although it is not infallible. Sometimes, it sees enemies where there are none and responds in an exaggerated and uncontrolled way against substances that are not harmful, such as a peach or the pollen of a flower. This is, in fact, how allergies develop, ailments that have skyrocketed across the planet in recent decades. According to the World Health Organization, between 20% and 25% of the population suffers from an allergic disease to foods, medications or environmental elements, such as the pollen of some plants. And although they are more common in high-income countries, there is no region on the planet that is immune: experts estimate that by 2050, half of the world's population will suffer from some allergy. Climate change, pollution, globalization and Western lifestyles have fueled this explosion of cases, the appearance of new allergens and the democratization of a pathology once associated with the upper classes and rich countries.

Allergies are, in the words of Tomás Chivato, Vice President of Science of the European Academy of Allergy and Clinical Immunology (EAACI), “a mistake of the immune system.” The army of the human body reacts abnormally to a non-harmful element and secretes substances that cause a range of symptoms, which can range from conjunctivitis to nasal congestion, asthma or skin rashes, among others. In the worst case, contact with an allergen can cause anaphylaxis, which is a generalized and potentially fatal allergic reaction throughout the body. Allergic rhinitis, atopic dermatitis and bronchial asthma are usually, along with food allergies, the most common conditions. “In Western countries it is a real epidemic: in Europe there are 150 million people with some allergy. It is a public health problem,” says Chivato. According to the

Global Atlas of Allergies

, written by the EAACI, these pathologies are already affecting about 1 billion people in the world and by 2050, their prevalence is expected to reach 4,000.

This rising phenomenon, according to the experts consulted, is multifactorial. There may be a certain genetic predisposition - there are genes involved and if both parents have an atopic load, there is up to an 80% chance that the offspring will also develop allergies - but scientists also point to the type of life, the environment and the environment. “The exposome [all the environmental factors — diet, lifestyle, microbiome, obesity, environment… — with which a human being comes into contact throughout their life] is conditioning and increasing this atopic predisposition (to respiratory allergies, foods and atopic dermatitis). It influences the immune system, promoting allergies,” explains Joan Bartra, head of Allergology at the Hospital Clínic of Barcelona.

Pollution and climate change, for example, go hand in hand and work against each other. A review by Indian researchers points out that all these environmental changes can cause an increase in pollen production and change its molecular characteristics to increase its allergenic properties. Chivato agrees: "Plants are also stressed and produce defense proteins against the aggression of pollution and this favors food allergies, such as tomato, which was not used to be seen." The allergist, who is also dean of the Faculty of Medicine at the CEU San Pablo University, also insists that climate change is “an essential factor” in the rise of allergies: “The month of January that we have had is not normal.” had, so hot. Thus, plants are confused by the season and begin to reproduce earlier,” altering—and extending—the traditional allergy season.

Western lifestyle habits and changes in dietary patterns are another piece of the puzzle. Experts suspect that the excessive use of antibiotics, the increase in cesarean sections or the impoverishment of the diet, with the extreme consumption of ultra-processed and high-fat products, has favored a decrease in microbial diversity in the intestine, facilitating, in turn, time, a greater sensitivity to certain substances and causing allergies. “Food and what you breathe have an impact on the microbiome [the ecosystem of microorganisms that populate the intestine] from early childhood. And it is a window of opportunity for the immune system to orchestrate its response. We know that the microbiome has a great impact on immune regulation and an alteration there is impacting a disorder of the immune system,” says Bartra. Along the same lines, Chivato highlights the key role of the decline in breastfeeding, since its practice makes the development of food allergies and atopic dermatitis more rare.

“Allergies are a toll that we have to pay for the progress in quality of life in Western countries.”

Tomás Chivato, Vice President of Science of the European Academy of Allergy and Clinical Immunology

Also on the table is the hygiene hypothesis, which associates the appearance of allergies and other inflammatory ailments with less exposure in childhood to certain microbes. “No one is born allergic. There is an allergic trend and the first disease that usually appears is atopic dermatitis and a clear factor is washing children with such aggressive products,” exemplifies Chivato. Studies in Germany and Switzerland with children raised in cities versus those who grow up on farms and rural environments show that urban children had more allergies than rural children. Likewise, children raised in homes with pets also had a lower risk of developing allergic rhinitis. “Our body is prepared to fight against parasites, but in the Western world they have decreased and we have begun to fight against pollen. It is an evolution of years due to the lack of infections. Allergies are a toll that we have to pay for the progress in the quality of life in Western countries,” reflects the vice president of the European academy.

Globalization, with migratory movements, the entry of invasive animal and plant species and the export of food or customs from one place to another, has facilitated what experts call “the democratization of allergies.” “These pathologies have existed since man was a man, but in the 19th century, those with allergies could be counted on the fingers of one hand and they affected the upper classes. Now, with industrialization, it affects all classes,” says Chivato. Pollution in more disadvantaged regions, for example, has accelerated the appearance of cases of asthma and rhinitis. Allergies are no longer just diseases of rich countries.

New allergens: dyes, velutinas and more anisakis

All this breeding ground has also generated the appearance of new allergens. Like the Asian wasp (velutina), an invasive species that is already established in Spain. “Allergy affects children and young people more, but we see more and more adults developing new allergies. Decades ago, for example, it was rare to see a reaction to cypress trees and now, with the rise of this plant in home gardens, we see more allergies to this pollen,” says Chivato. In

The Book of Allergic Diseases

, published by the BBVA Foundation and the Spanish Society of Allergology, the appearance of allergies to hairdressing dyes, such as paraphenylenediamine, is also reported; to new pets, such as hamsters or ferrets; and plants native to the American continent, such as ragweed, which, with intercontinental flights, has settled in Europe.

Another paradigmatic example has been the growing allergy to anisakis, more common in inland areas than on the coast, Chivato clarifies: “Before it did not exist because the fish was cleaned on boats, but since now it is cleaned later, the larvae of the parasite They spend more time in the digestive system of the fish and can migrate from there to the area that we eat. And if it is undercooked, we can eat a larva.” Bartra specifies that everything that changes exposure habits has a direct association with what one may be allergic to: “With cultural fusion cuisine, new foods are introduced and there are more candidate sources of allergens. It was rare for our grandparents to eat Brazil nuts, but now they do and we already have people with severe allergies to this food.”

These exaggerated reactions of the immune system do not usually impact survival, but they can greatly reduce quality of life. And an example of this is, for example, eosinophilic esophagitis, an inflammatory disease that affects the esophagus and is closely linked to food allergies. “It goes hand in hand with patients who have this atopy and when you look at the protagonists of this inflammation, it is very similar to what is in the substrate of allergic asthma. It is like a version of asthma, but in the esophagus,” says Bartra. Not only do allergic people suffer from it, but up to 80% of patients have some history of atopic disease, explains Sergio Casabona, a specialist in Digestive Medicine at the La Princesa University Hospital: “There are patients without allergies who suffer from this disease, but they tend to be milder cases. Those whose immune response is already more severe are the most complex cases,” explains the doctor, who has more than half a thousand patients with this condition in his hospital.

Allergists warn that this disease has increased substantially in recent years and can greatly affect lifestyle habits. The spectrum of clinical manifestations is very broad and so is the severity, admits the Clínic allergist: “There is an inflammation process and it involves a remodeling of the structure of the esophagus. There is a sort of stiffening that makes the esophagus narrower and mechanically it does not act with the necessary propulsion to bring food to the stomach.”

The ordeal of eating

Carlos Solas, 34 years old, is in one of the worst scenarios of this complex pathology. “Every time I eat I face a battle,” he summarizes. Since he was little, he had environmental allergies to olive pollen and grasses, and he knew that he couldn't eat seafood because it made him sick. But the disease did not show its face until 2009, with the first choking: “The first was on a piece of meat, but I was like this for five more years, with choking very frequently that they attributed to anxiety, stress,” he says. In 2014, two anaphylactic shocks precipitated the real diagnosis: “They did allergy tests and I had sensitivity and allergies to more than 12 foods.” A year later, it was confirmed that he suffered from eosinophilic esophagitis and he began the journey in search of a treatment: “They took away eight foods: I didn't eat wheat, rice, fish, shellfish, nuts or milk... I went on an avoidance diet. for eight years, but I didn't improve,” he says. Eating was agony: he had extreme chest pain, vomiting and dysphagia. “We want to swallow, the worse the food stays there, it doesn't go down. 2020 was the worst year of my life, I couldn't even swallow my saliva. I lost 20 kilos. My esophagus had tremendous inflammation,” he recalls.

Casabona explains that it is usually a protein in a food that causes esophagitis, but the foods involved cannot always be identified. It can be treated with avoidance diets, high-dose omeprazole, corticosteroids and there are also biological treatments on the horizon, but in Solas' case, almost nothing worked. She had to undergo two esophageal dilations, she still has a problem and, although she has now found a corticosteroid with which she has improved her quality of life, the disease still weighs too much on her daily life. “After so much choking, you also face the emotional factor. The illness affects you by not traveling, not having a social life... I have become a more solitary person and now I am coming out of depression. Now I don't choke as much, but it still happens,” she assumes. Solas warns of the need to raise awareness about this ailment and to do more research into it because, with the rise of allergies, “it will become more and more common.”

Immune system errors

in

the form of allergies will continue to increase. And although there has been improvement in diagnosis and treatment, the great pending task continues to be prevention. The scientific community discusses whether to expose children to potential allergens sooner or later and what window of opportunity there is to impact the immune system, but there are still “no conclusions,” Bartra admits: “We do not know how to intervene in this regulation of the system. immune. We don't know where that window of opportunity is, with what burden... There is a lot of fabric left to cut.”