Recent studies have suggested that null genotype of GSTM1 may be associated with risk of cancer and other diseases related to oxidative stress; individuals with GSTM1 null allele polymorphism have been observed to be at greater risk for cancers of the breast, prostate, cervix, skin, and mouth, as well as atopic asthma [22–27]. This evidence concerns the gene GSTM1 and atopic asthma.