Epidemiological evidence on the relationship between IL4 single nucleotide polymorphisms (SNPs) and allergic rhinitis is limited. We conducted a case-control study to investigate this issue in young adult Japanese women. Included were 393 women who met the criteria of the International Study of Asthma and Allergies in Childhood (ISAAC) for rhinoconjunctivitis. Controls were 703 women without rhinoconjunctivitis based on the ISAAC criteria who had not been diagnosed with allergic rhinitis and/or asthma by a doctor. Compared with the TT genotype of IL4 SNP rs2227284, the GG genotype, occurring in 10.2% of control subjects, was significantly inversely associated with the risk of rhinoconjunctivitis: the adjusted OR was 0.60 (95% CI: 0.37-0.98). There were no significant relationships between SNP rs2243250, rs2070874, or rs2243290 and rhinoconjunctivitis. None of the haplotypes were significantly related to rhinoconjunctivitis. A significant inverse relationship between the combination of the TG and GG genotypes of SNP rs2227284 and rhinoconjunctivitis was observed in women who had never smoked, but not in those who had ever smoked (P for interaction=0.11). This is the first study to demonstrate a significant relationship between IL4 SNP rs2227284 and rhinoconjunctivitis. Smoking may modify the relationship between SNP rs2227284 and rhinoconjunctivitis.
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