Are more and more people susceptible to allergies because the environment is too clean?

Why are people becoming more and more susceptible to allergies? In fact, this is a grand question and there is currently no "precise and comprehensive" answer.

Despite this, there is a theory that is widely accepted by researchers - the "hygiene hypothesis", which states that the better the hygiene conditions, the fewer infections children have in their early years and the greater the chance of developing allergies in their later years.

Just because it's too clean?

The British Broadcasting Corporation (BBC) recently conducted follow-up interviews with two families of children with allergies in the UK, trying to prove the "hygiene hypothesis."

The first family is a family of four. An 8-year-old boy named Joe lives with his parents and sister. He suffers from severe asthma, hay fever, eczema, and is allergic to some nuts, pets and dust.

Another family's little patient is named Morgan, who is 4 years old and suffers from allergies. As well as suffering from severe eczema and hay fever, he cannot eat any nuts, dairy, soy, kiwis, avocados, bananas and is allergic to rubber, cats, dogs and horses.

The study showed that both families had "too few" types of bacteria in their living environments and on their members. In developed Western countries, with changes in lifestyle and improved sanitary conditions, most families are unable to "cultivate" a rich bacterial flora, making it difficult to induce children's original immune function. The Joe and Morgan families spend an average of 91% of their time indoors, with little contact with outdoor air, garden soil, or small animals.

In contrast, in some developing countries, especially those primitive areas that still retain traditional hunting customs, scientists have found that The local residents now carry a diverse range of bacteria, and only one in every 1,500 people suffers from allergies. In the UK, one in three people suffers from allergies.

Data from the World Allergy Organization shows that over the past 40 years, the number of people suffering from allergic asthma worldwide has increased at an alarming rate, with an average increase of 50% every ten years.

Caesarean section related?

In recent years, children with allergies like Joe and Morgan have become increasingly common in Western countries. The number of American children with food allergies has increased by about 20% in the past 10 years, with the number of children allergic to peanuts alone doubling.

In 2013, researchers in the United States found that children born by cesarean section have a higher risk of allergies than those born vaginally. The researchers evaluated more than 1,200 newborns at 1 month, 6 months, 1 year and 2 years old, and found that by the age of 2, if these children were exposed to common household allergens such as pet dander and mites, the proportion of children born by cesarean section suffering from allergies was 5 times that of children born naturally.

Experts say that early exposure to a microbial environment affects children's immune system development and allergy onset, and that the maternal bacteria that children are exposed to during vaginal delivery may have a beneficial effect on their immune system. When exposed to allergens, children born by cesarean section are more likely to produce immunoglobulin E, which is associated with the onset of allergies and asthma. The proportion of children born by caesarean section in developed countries is much higher than it was 20 years ago, which may explain from one perspective why children today are more "sensitive" than their parents.

Additionally, one study found that taking antibiotics too early could increase a child's risk of developing eczema by 40 percent.

Dietary habits and preferences can also affect a child's chances of developing allergies. One study compared the daily food and gut microbiota of 15 children in Florence, Italy, and a small village in Burkina Faso. The results showed that the daily diet of Italian children was rich in sugar and animal fats and high in calories, while African children mainly ate vegetarian food; the intestinal flora types of children in the two places were therefore very different, and the bacterial species in African children were more diverse than those in European children.

Beneficial on the farm

After decades of research on allergies, experts learned an unexpected discovery from a Swiss country doctor many years ago: children living on traditional farms in Europe never suffer from hay fever or hay fever. In 1998, this expert, together with experts from many European countries including Germany, Austria and Switzerland, began a large-scale study of traditional European farms. The research took several years.

Experts have found that farm children are less likely to develop allergies because they and their families maintain a traditional farm lifestyle. She further summarized the "farm effect" into three key elements: contact with livestock (especially cows, dogs, and poultry such as chickens and ducks), contact with grass, and drinking fresh milk. "Humans have been interacting with farm animals for thousands of years, so there may be some evolutionary mechanism that allows the human immune system to function normally," the expert said.