In particular, single nucleotide polymorphism (SNP) alleles in the transient receptor potential ankyrin 1 (TRPA1), transient receptor potential vanilloid (TRPV1), toll-like receptor 2 (TLR2) and toll-like receptor 4 (TLR4) have been associated with asthma susceptibility and symptom severity 3–7. This evidence concerns the gene TLR4 and asthma.