Microorganisms that influence the body's reaction to food

An international study involving the Francisco de Vitoria University (UFV) has found that microorganisms present in saliva can break down allergenic proteins and reduce the severity of allergic reactions.

Food allergies affect millions of people worldwide, and in the case of peanuts, even tiny amounts can trigger severe, life-threatening reactions, such as anaphylaxis. But a new international study points to an unexpected ally in the fight against this problem: the bacteria that naturally live in our mouths.

The study, published in the scientific journal Cell Host & Microbe and reviewed in Nature(https://www.nature.com/articles/d41586-026-00668-9), has shown that certain bacteria found in saliva can break down peanut proteins responsible for allergic reactions, thereby reducing their ability to trigger an immune response.

The study was led by scientists from the Institute for Health Research at La Princesa University Hospital (Madrid) and McMaster University (Canadá), including Dr. Rodrigo Jiménez-Saiz, a professor affiliated with the Bachelor's Degree Biomedicine at Francisco de Vitoria University.

We are gaining a better understanding of how the microorganisms that live in our bodies also influence how we react to food. In this study, we have seen that “some bacteria naturally present in the mouth can break down peanut proteins responsible for allergic reactions, thereby reducing their ability to trigger the immune system,” explains Dr. Jiménez-Saiz.

Bacteria capable of “deactivating” the allergen

The research team discovered that bacteria of the genus Rothia, which occur naturally in the oral cavity, have the ability to break down highly allergenic peanut proteins.

When these proteins are broken down by bacteria, their ability to activate cells involved in the allergic reaction is reduced.

In laboratory experiments, peanut proteins that had been previously processed by these bacteria caused significantly less activation of allergy-triggering cells than intact proteins.

"The findings suggest that 'the oral microbiota may act as the first point of contact between food and the immune system,'" the expert notes.

Editado_Equipo investigación Hospital La Princesa Bacteria in the mouth may reduce allergic reactions to peanuts, according to a study involving the UFV Study at the Universidad Privada Madrid

Rodrigo Jiménez-Saiz (bottom left), a professor at UFV, alongside the research team at La Princesa Hospital in Madrid.

An effect that is also observed in animal models

The researchers wanted to determine whether this phenomenon could have real effects on the body. To do so, they used mouse models colonized with bacteria of the genus Rothia.

The results showed that animals carrying these bacteria developed less severe allergic reactions after consuming peanuts than those that did not.

In addition, when peanuts that had been pre-digested by these bacteria were administered, the intensity of the reaction also decreased.

These findings suggest that the microbiota may alter the way the body recognizes food allergens.

Why do some people react worse than others?

One of the most difficult questions to answer in the field of food allergies is why two people who are allergic to the same food can experience very different reactions.

To investigate this issue, the researchers analyzed saliva samples from patients with peanut allergies at hospitals in Boston and New York.

The analysis revealed that patients with a higher abundance of bacteria capable of breaking down peanut proteins had a higher tolerance threshold for the allergen—that is, they needed to ingest a larger amount before developing symptoms.

This finding could help explain some of the differences in the severity of reactions among patients.

Editado_Placa con bacterias humanas degradadoras de cacahuete Bacteria in the mouth may reduce allergic reactions to peanuts, according to a study involving the UFV Study at the Universidad Privada Madrid

Plate containing human bacteria that break down peanuts.

A new approach to treating food allergies

Currently, the main treatment for food allergies involves strictly avoiding the food that triggers the reaction. However, the study’s findings open up a potential therapeutic approach based on modulating the microbiota.

According to the researchers, increasing the presence of beneficial bacteria capable of breaking down allergens—for example, through specific probiotics—could help reduce the severity of allergic reactions in the future.

This breakthrough is particularly significant given that between 1% and 2% of the world’s population may be allergic to peanuts, one of the foods most commonly associated with anaphylaxis.

As Professor Rodrigo Jiménez-Saiz puts it: “Understanding how the immune system, food, and the bacteria living in our bodies interact can lead to new strategies for preventing or reducing food allergies.”

The Bachelor's Degree Biomedicine at Francisco de Vitoria University promotes an educational program that bridges basic science with applied research and the major challenges facing healthcare. Participation in programs such as this highlights UFV's role in generating knowledge with clinical and social impact, and reinforces a research approach focused on better understanding disease in order to respond more precisely to people's needs.