Exclusion diets are everywhere. Parents who try to calm their children’s eczema’s crises with influencers who stop consuming gluten and dairy products in pursuit of the “clean eating”.
But researchers show that excluding food from your diet can subtly change your immune response when you consume them again. In some people, especially in those with eczema or having had food allergies in the past, this loss of tolerance can cause dangerous reactions, even anaphylaxies, severe allergic manifestations that can be very serious, at the time of the reintroduction of banned food.
This risk is often overlooked with the growing popularity of exclusion diets. In the United States, for example, the National Center for CDC health statistics (Centers for Disease Control and Prevention, Center for Disease Control and Prevention) declare that Americans follow more of these plans than ever. Some do it because they are celiacs or suffer from irritable colon syndrome, others to reduce bloating, fatigue or joint pain. Tenders on social networks like #Cleaneating have only intensified the attraction of such regimes. In 2024, more than half of Americans said to follow a special diet, compared to 38 % in 2019.
However, for the immune system, regular exposure to food proteins makes it possible to maintain a state of tolerance. This state can be disturbed when these foods disappear from the menu for too long. Understanding how and why this change occurs is essential in order to know when exclusion diets can help, and when they are dangerous.
“The role of the intestine is not enviable,” says Brian Vickery, head of the Department of Allergies and Immunology and Director of the Food Allergies program at the Emory Children’s Hospital in Atlanta. “He must identify and respond to a constant flood of environmental stimuli which can be both dangerous and healthy. »»
The digestive tract, which contains more immune lymphocytes than no other part of the body, is faced with hundreds of billions of microbes and more than 30 kilograms of food protein each year. And yet, he manages to defend himself against harmful invaders while ignoring foods that have no danger and beneficial bacteria.
This balancingist issue is based on oral tolerance, a process during which immune responses to ingested food proteins are actively removed, which starts harmful reactions, such as food allergies. Although we do not fully understand the underlying immune mechanisms, this last study indicates that they begin with antigen presenting cells, which capture food antigens in the intestine and inhibit the reaction of close t lymphocytes. This signal generates T lymphocytes regulating specific antigens, which soothe the response of the immune system to food proteins.
“The intestine is important to the initial establishment of tolerance,” explains Michael Pistiner, director of the Department of Food Allergies, their prevention, explanation and treatment within the Massgeneral Children’s Hospital. “If you are not already allergic, an early introduction to food can help support tolerance in infants and prevent the development of food allergies in them. »»
This protection does not disappear at the end of childhood. Continuous and regular exposure to food contributes to the maintenance of oral tolerance throughout life. Recent research has been carried out in patients with food allergies according to the treatment of oral immunotherapy. It is a treatment during which ever larger doses of allergenic foods are consumed orally. These studies point out that continuous ingestion is often necessary for the maintenance of a desensitized state. Conversely, there is evidence that exclusion diets in some can destabilize oral tolerance and encourage the immune system to develop allergies.
For parents of children suffering from eczema, it is common to suspect that certain foods worsened crises. Many turn to exclusion diets with the hope of discovering responsible food. But studies have revealed a hidden risk. Anne Marie Singh, Professor and Chef of the Division of Allergies, Immunology and Rheumatology of Wisconsin-Madison University, and her colleagues, evaluated around 300 children suffering from eczema and following an exclusion regime.
“We discovered that, if we suppressed the food from their diet, its reintroduction caused a significant increase in the risks of allergic reactions, including immediate and potentially severe reactions,” said the scientist. The results were undoubtedly: almost one in five children (19 %) developed new immediate allergic reactions when the excluded foods were reintroduced, even if it had no history of such immune responses. Most were benign, but an alarming percentage of 30 % of the reactions were severe and classified of anaphylaxies.
The danger is not limited to children. During a separate study carried out on thirty adults who had developed food allergies to foods they tolerated in the past, 70 % followed exclusion diets beforehand. Half experienced anaphylaxies, and the vast majority of them (80 %) suffered from pre -existing allergies: environmental allergies, asthma or eczema. For patients without allergic history, the risk was much lower.
If you plan to start an exclusion diet, experts explain that the least risky approach depends on your risk level. If you are a person entering a risk category (pre -existing children or allergies), consult a healthcare professional before starting this diet.
“The more allergic you are, the more an exclusion diet could be a problem,” explains Anne Marie Singh. Michael Pistiner adds that “in infants suffering from eczema, exclusion diets can be harmful, especially during this important period of their lives, at the time of diversification”. Experts also recommend that children following exclusion regimes are closely followed by doctors to ensure nutritional adequacy and normal growth.
The duration is also important. A shorter exclusion phase leaves less time for oral tolerance to disappear. Anne Marie Singh points out that “two to four weeks of exclusion could be sufficient to observe a real difference, while being short enough not to risk any allergic reaction to the reintroduction of the food”.
In some cases, completely excluding a food is not necessary. If the symptoms are moderate, maintaining a small tolerable proportion of the food in its diet can help maintain tolerance while soothing discomfort, adds Anne Marie Singh.
