Background: Bronchiolitis is the most common infection leading to hospitalization in infancy. Interleukin-10 (IL-10) is an anti-inflammatory cytokine, and in our previous study, IL10 gene rs1800896 (− 1082A/G) polymorphism was associated with viral etiology of infant bronchiolitis. The objective of this study was to evaluate the associations between IL10 single nucleotide polymorphisms (SNPs) at rs1800890 (− 3575A/T), rs1800871 (− 819C/T) or rs1800872 (− 592C/A) either alone or combined with the SNP at rs1800896 (− 1082G/A), and the etiology and severity of infant bronchiolitis.

Methods: Data on four IL10 SNPs were available from 135 full-term infants, hospitalized for bronchiolitis at age less than 6 months, and from 378 to 400 controls. Viral etiology was studied, and oxygen support, feeding support and the length of stay in hospital were recorded during bronchiolitis hospitalization.

Results: Infants with rhinovirus bronchiolitis had the IL10 rs1800890 variant AT or TT genotype less often (18.2%) than controls (63.3%, P = 0.03), and likewise, had the IL10 rs1800896 variant AG or GG genotype less often (27.3%) than controls (65.5%, P = 0.009). Twenty-eight infants with bronchiolitis had the variant–variant G_rs1800896 T_rs1800890 haplotype, and none of them had rhinovirus infection. The IL10 rs1800871 or rs1800872 genotypes showed no associations with viruses. No association was found between any genotypes and bronchiolitis severity measures.