Peanut allergy: microbiota makes a difference

Allergies

The severity of a peanut food allergy does not depend solely on the level of specific IgE antibodies. A study shows that oral and gut bacteria, such as Rothia, break down the allergen and modulate anaphylaxis severity. Microbiota may therefore help explain why the same allergy causes reactions of very different intensity from one patient to another.

Peanut allergy: microbiota makes a difference

About this article

Created 27 August 2026

Updated 03 September 2026

Bacteria capable of disarming allergens

In mice, researchers¹observed that the presence of gut bacteria changes how the body responds to peanuts. The group of mice with rich and diverse gut microbiota broke down the two proteins responsible for most allergic reactions, Ara h 1 and Ara h 2, far more effectively than mice raised with little or no gut microbiota. As a result, fewer intact allergens entered the bloodstream and the allergic reaction triggered after exposure was significantly less intense. Conversely, a second group with limited microbial diversity showed more markers of a severe reaction.

Ara h 1 and Ara h 2

The two peanut allergen proteins most often recognized by the immune system of people with allergies.

Immune system

All the cells and molecules that protect the body against infections, abnormal cells and foreign substances. In an allergy, IgE and mast cells are involved in recognizing the allergen and triggering the reaction.

Severe allergic reaction (IgE-mediated anaphylaxis)

Acute, generalized reaction that can be fatal within minutes, triggered when an allergen binds to IgE attached to mast cells, causing the rapid release of inflammatory mediators.

The bacterial genus Rothia stood out in this research. It is naturally present in the human mouth and small intestine. In the laboratory, it breaks down the two main peanut allergens at specific sites, preventing IgE antibodies from recognizing them. Less recognition means less activation of mast cells, the immune cells responsible for allergy symptoms.

IgE (Immunoglobulin E)

Antibody responsible for immediate allergic reactions, produced by the immune system when it comes into contact with an allergen.

Mast cells

Immune cells that release inflammatory substances during an allergic reaction.

Microbiotal bacteria (enzymatic breakdown of food proteins)

Microorganisms in the oral cavity and intestine that use proteolytic enzymes to break down food proteins resistant to human digestion, including peanut allergens.

Some Staphylococcus strains have a similar effect, but not all of them. The study shows that two strains of the same species can behave in opposite ways, with one efficiently breaking down the allergen and the other not at all.

Preventing peanut allergy thanks to the microbiota?

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A finding confirmed in patients with allergies

The researchers then analyzed saliva samples from 19 patients with peanut allergy. These children, ages 1 to 14, were studied before starting oral immunotherapy treatment. The group of patients that tolerated the highest allergen doses during controlled tests harbored more bacteria capable of breaking down peanuts, including bacteria from the Rothia genus, regardless of their blood levels of Ara h 2-specific IgE. They therefore showed greater allergy tolerance. This observation was then identified in 120 children monitored in an independent study, further strengthening its credibility.

These findings could eventually help better estimate the reactivity threshold and personalize treatment, but they cannot predict the severity of a child’s allergic reaction.

More than 70% of peanut allergies persist over time. This makes the search for new ways to limit the severity of accidental allergic reactions particularly valuable. For affected children and their families, the goal would be to reduce the risk associated with unintentional exposure.These findings still need confirmation through larger studies before any clinical application, but they open up a serious avenue: a microbiota that protects or, conversely, increases exposure depending on the microorganisms it contains. A promising discovery for potential future treatments.

Source

^{1. Sánchez-Martínez E, Rondeau LE, Garrido-Romero M, et al. Microbial metabolism of food allergens determines the severity of IgE-mediated anaphylaxis. Cell Host Microbe. 2026;34(4):600-619.e9.}