Zimmerman et al. showed using microarray analysis that in both ovalbumin-sensitized and Aspergillus fumigatus-sensitized mice, ARG1 mRNA levels were upregulated 40-fold and 20-fold, respectively, whereas ARG2 mRNA levels were upregulated only 3-fold in both models of allergic asthma [5]. Here, ARG1 is linked to allergic asthma.