Allergic rhinitis: the first months of life are key

Rhinitis, and more generally respiratory disorders accompanied by a whistling sound (wheezing, asthma²⁵), are common in babies and children²⁶. Several studies have addressed the link between respiratory microbiota and onset of these disorders and have demonstrated the direct influence of the environment and lifestyle²⁷.However, the precise link between the nasal microbiota of infants and allergic diseases such as rhinitis and wheezing–which is expressed by the emission of a whistling sound on expiration and/or inspiration–had never been studied up until now. This has now been done by an international comparative study whose results were published recently²⁸.

Very distinct microbial diversity

The development of the nasal microbiota of three groups of children was analyzed and compared very regularly over the first eighteen months of life: 23% of subjects were affected by rhinitis alone, 28% by rhinitis associated with wheezing and the others were in good health. Result: their nasal microbiota developed differently depending on whether or not they had rhinitis, particularly when it was accompanied by wheezing. As these differences were observed very early (sometimes at three weeks old), and most importantly before the onset of clinical symptoms, the researchers deduced that the nasal microbiota played a crucial role in the development of this respiratory disease. More specifically, according to the literature, the nasal microbiota of infants is dominated by three large bacterial groups (Actinobacteria, Proteobacteria and Firmicutes²⁹). This was confirmed by the study. Another result that agrees with the literature³⁰ is that the bacterial diversity in the nasal microbiota of the infants with rhinitis (with or without concomitant wheezing) was reduced. The increased abundance of certain bacteria was thus associated either to allergic rhinitis and concomitant wheezing (Oxalobacteraceae, Aerococcaceae), or to the composition of the healthy flora of unaffected children (Corynebacteriaceae and early nasal colonization by bacteria belonging to the Staphylococcus family)In other words, the nasal microbiota incorporates a “microbial signature” that reflects the respiratory pathology and its severity level.

A predictive factor for rhinitis

These data show that some of the bacteria involved protect against respiratory diseases in infants²⁵. They also confirm that specific nasal microbiota profiles before the age of eighteen months may favor the early development of allergic rhinitis and wheezing. Another observation: one child out of five suffering from rhinitis in the study was still affected at the age of five, while those without rhinitis throughout their very early childhood did not develop it subsequently. Therefore whether or not a child suffers from rhinitis at eighteen months old has a predictive value in this matter. In addition to the potential development of new therapeutic strategies, these results could allow for a better understanding of the role of the nasal microbiota in asthma, a disease which is closely associated with rhinitis.