Food Allergy

Food allergy is an adverse immune reaction to certain food or food types that is usually harmless to human beings. It mostly manifests as a reaction in the skin as well as the digestive or respiratory systems. The allergies differ vastly across ages and demographics. Younger children, especially in developed countries, have a high rate of food allergies of about 4–11% compared to a prevalence in adults of 0.2–4.1%. The allergen (the substance that causes the allergy) also differs geographically, with peanuts being more prevalent in developed countries and milk and eggs being universal.

Oral Tolerance

Food allergies occur because the body’s defense system gets triggered by certain ingredients in the food that it thinks is harmful to the body. This can be detected by the increase in a specific type of defense proteins in the body. The best method to prevent allergy has been to completely avoid the allergen. However, in the long run, this could be an issue due to a potential lack of specific nutrition or a severe reaction due to a chance contact with the allergen. Instead, the goal would be for the body to not react to the food allergens, which is termed as oral tolerance. In case of certain allergies, oral tolerance is sometimes arrived at naturally. For example, young children with food allergies like milk and egg often outgrow them by the time they enter school. Another way to restore oral tolerance is by introducing the allergen in gradually increasing doses. In a study to restore egg tolerance using this method, it was found that, after 6 months, 9 out of 10 children achieved tolerance while in the group without treatment no children achieved tolerance. Unfortunately, these methods are not yet standardized and also long-term tolerance has not been studied.

To understand further methods to avoid allergy or restore tolerance, we need to look closer at what makes the food an allergen.

Different Targets for Oral Tolerance

Immune System in the Intestines

The intestine has a complex job of ensuring that the good part of the food enters the body, while any harmful substances like infectious agents are gotten rid of. For this job, the intestine works closely and maintains a balance with the immune system. In the case of food allergy, there can be an error in the behavior of the immune system which causes the harmless molecules to be “seen” as harmful. There can also be an imbalance in the immune cells present due to different triggers. To combat this, clinical therapy is used to retrain the immune system to treat the allergen as dangerous. The therapy also helps restore the balance in the different immune cells towards encouraging oral tolerance.

Gut Microorganisms

From when a child is born, microbes start accumulating in the gut. These microbes help shape gut health by helping maintain a good barrier and communication with the immune system. These same functions make the microbes critical to avoid food allergies, too.

In this context, a study indicated the importance of breastfeeding, since infants receive 27.7% of breast milk bacteria and 10.3% of bacteria from the area around the nipple. Another study showed that this bacteria from the breastmilk helps reduce the risk of food sensitization in the baby when they are a year old.

The introduction of solid food and potential allergens at an early age is being debated. While the gut and immune system might not be ready for an early introduction (below 6 months) to food, studies show that peanuts being introduced early helps reduce allergy towards them. Only 1.9% of children who started consuming peanuts when they were less than a year old were allergic at 5 years compared to 13.9% in the group that avoided peanuts. More research needs to be done in different demographics to understand the best time to introduce the allergens.

Processing Method of Food

The allergic response to food is found to depend, in some cases, on the way the ingredient is processed. While the immune changes and the different processes need to be extensively researched, there are already many reports on egg-allergic and milk-allergic people being tolerant to baked egg and baked milk, respectively. The more interesting result is that over time, some people who are tolerant to the processed forms of egg and milk can become tolerant to the raw form. This provides yet another natural way of reaching oral tolerance to certain food allergies. However, those who are not tolerant to the baked or processed forms of milk and eggs should be treated carefully when trying any such therapy, as they can have adverse reactions.

What Did We Learn?

Instead of complete food allergen avoidance, people with food allergies can train their bodies towards oral tolerance. This can be achieved – naturally, through the gradual introduction of allergens, using immunotherapy, improving diversity in gut microorganisms or by introducing a processed form of food allergens. It is important to discuss the best suitable oral tolerance therapy with the doctor based on the specific food allergy and health condition of the patient.