Research suggests that microbes in the gut and mouth could determine whether peanut allergies lead to mild or life-threatening responses. A study on mice and humans points to specific bacteria that might reduce anaphylaxis risks. Scientists propose probiotics as a potential treatment to lessen severe reactions.
Peanut allergies arise when the immune system misidentifies proteins in the legume as threats, triggering excessive antibodies and inflammation. Symptoms range from itching and swelling to vomiting, with severe cases causing anaphylaxis, which involves breathing difficulties and can be fatal.
Rodrigo Jiménez-Saiz at the Autonomous University of Madrid in Spain and his team investigated the role of microbiomes in this variability. They noted, “There’s a big question around why some patients are more susceptible to more severe reactions.”
In experiments, researchers introduced small amounts of peanut into the stomachs of three mouse groups: germ-free mice, those with minimal microbiome diversity, and those with a typical healthy microbiome. After 40 minutes, the germ-free and minimal-microbiome groups showed higher intestinal levels of key peanut allergy proteins, Ara h 1 and Ara h 2, compared to the diverse group.
The diverse microbiome mice had elevated levels of Rothia bacteria, particularly the Rothia R3 strain, which aids in digesting peanuts. To test its impact on anaphylaxis, the team induced peanut allergies in mice with minimal microbiomes and implanted Rothia R3 in half. Following peanut exposure, all mice experienced anaphylaxis, but those with Rothia R3 saw only a 2 percent drop in body temperature on average, versus 3.5 percent in controls. These mice also had about half the blood levels of the immune molecule MMCP-1, which rises during anaphylaxis.
Mohamed Shamji at Imperial College London commented, “The findings are compelling.” He added that similar changes in humans could reduce anaphylaxis severity.
In a human study of 19 peanut allergy patients, those with greater peanut tolerance had higher Rothia levels in their saliva, indicating its role in both gut and mouth.
Shamji stated, “The need for something like this is huge,” highlighting potential to ease fears of accidental exposure and improve oral immunotherapy. The team plans a clinical trial testing Rothia probiotics against a placebo before low-level peanut exposure.
The research appears in Cell Host & Microbe (DOI: 10.1016/j.chom.2026.02.013).
