Allergies are a huge burden on the healthcare system and the economy. There are more than 520 million people in the world with food allergies, two million in Spain (mostly children, but 3% adults). Experts warn that there is a growing trend in food allergies. The question is what causes it.

on the rise. Cases have increased by up to 50% in the last decade, with a 700% increase in hospitalizations for anaphylaxis in the USA. Between 2013 and 2019, there was a 72% increase in the number of hospitalizations in Europe. While the World Allergy Organization (WAO) suggests that more than 170 foods are associated with allergic reactions, there are typically 14 major allergens, with peanuts, eggs and tree nuts being the most common.

What is an allergy? Before going into details about the possible hypotheses that triggered the phenomenon, it is necessary to understand what an allergy is and why it happens. This is an overreaction of the immune system that produces an antibody called immunoglobulin E (IgE). This protein helps the immune system fight invaders. When it encounters them, it triggers the production of a hormone called histamine, which causes blood vessels to dilate, tissues to swell, the skin to itch, and the airways to wheeze, cough or sneeze in hopes of warding off the threat.

The problem is that even though the goal was to deal with parasites, our bodies started ringing alarm bells with benign things like pollen or peanuts. This can lead to severe cases, a reaction called anaphylaxis, in which blood vessels expand enough to cause a large drop in blood pressure and inflammation forces the airways to close. this can result in death.

Why is there more now? One of the hypotheses considered among experts is hygiene. As cities improve cleanliness and sanitation, food allergy rates have increased. The idea is that with fewer germs and parasites to fight everywhere, the immune system starts turning on harmless things like allergens. This is why rich countries have the highest allergy rates. That is, they increase as the standard of living rises.

The “old friends” theory. There are benign, even helpful bacteria that have evolved with humans and play an important role in the immune system: so-called “old friends.” As people spend more time in sterilized environments, they are less likely to encounter them again. That’s one reason why there’s a link between food allergy and babies born by cesarean section: Staying out of the birth canal means the baby isn’t ingesting the beneficial bacteria there. In Denmark, it has been shown that the more cats and dogs you have, the less likely you are to develop an allergic disease.

The first years are key. Babies’ immune systems are modifiable, and the first months of life are vital to managing these threats. A 2015 study called LEAP (Early Learning About Peanuts) concluded that the rate of peanut allergy was 13.7% in infants who avoided peanuts at the age of 5, and 1.9% in those who did not. Exposure at an early stage reduced the chances of developing allergies. So, telling parents to stay away from allergens may have made things worse.

Vitamin D deficiency. As vitamin D levels have fallen in all populations, food allergy rates have increased. This vitamin is produced when we are exposed to the sun, but it can also be obtained through diet. This suggests that people in rich countries who spend more time indoors have higher rates of food allergies than those who spend more time outdoors, according to some experts. Also, rates are higher in countries farther from the planet’s equator.

extreme treatments. While there is no cure for food allergies, innovative and slightly more extreme treatments such as desensitization are being tried. It consists in exposing the patient to small amounts of the allergen so that the body gradually ceases to perceive the protein as an invader and does not respond to it. Another research is immunomodulation: correcting the action of the immune system.

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