Preventing peanut allergy thanks to the microbiota?

For children, peanut allergy is a common but serious challenge. In Western countries, it affects almost 2% of children. ¹ Symptoms include breathing difficulties, swelling of the throat, diarrhea, nausea, skin rashes, and fainting. These symptoms vary in severity, but the most serious, anaphylaxis – an intense whole-body reaction – can prove fatal. ^2,3 Peanut allergy often manifests itself in early childhood, can be much more severe than other food allergies, and, unlike them, lasts into adulthood in 80% of cases. ¹

A link between the microbiota and food allergy?

What about the gut microbiota? For many years, it has been known that the microbial communities in the gut also play a key role in building the immune system. Recent research even suggests that the gut microbiota may be involved in the development of food allergies. Patients with food allergies present an unbalanced gut microbiota.

So, what happens in early childhood before allergies even appear? Researchers in the US set out to answer this question by analyzing the microbiota of 122 children from infancy to the onset of the allergy. Their aim was to better understand how the allergy develops, with the hope of one day being able to prevent it.

Tell me about your microbiota, and I’ll tell you your future allergy...

The researchers’ first finding was that patients who developed peanut allergy around the age of nine had a poorly diversified gut microbiota during their first months of life. Their microbial communities evolved more dynamically, with a less homogeneous distribution of species compared to the microbiota of children who did not develop the allergy, while their gut flora evolved more continuously and homogeneously over time.

Their second finding was that certain species of the Clostridium genus were more present in infants who did not have peanut allergy, while Streptococcus sp were more present in those who did. By the age of nine, Bifidobacterium, well-known beneficial bacteria, were more present in non-allergic patients.

In addition to the changes in abundance of certain bacteria being different between the two groups of children, the authors observed that the metabolites produced by the microbiota, i.e., the metabolome, were different in the children who developed an allergy. In particular, certain  SCFAs (sidenote: Short chain fatty acids (SCFA) Short chain fatty acids (SCFA) are a source of energy (fuel) for an individual’s cells. They interact with the immune system and are involved in communication between the intestine and the brain. Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020;11:25. ) , such as butyrate and isovalerate, decreased over time in the children who subsequently developed an allergy. Isovalerate is already known for its protective properties against allergy (asthma and atopy).

The development of peanut allergy was associated with changes in 139 metabolites, and particularly with a pathway for the metabolism of histidine, the precursor of histamine, a bioactive molecule released during allergic reactions.