GSTM1 and atopic asthma: This hypothesis is supported by a study in which the GSTM1 null genotype is associated with a decreased risk for asthma among atopic subjects [34] and another study investigating the effect of the positive and null-GSTM1 genotypes on allergen-induced oxidant stress, airway inflammation, and reactivity in vivo in adults with mild atopic asthma and without a regular asthma medication [35].