BALB/cJ mice were sensitized and challenged with OVA. AHR was assessed 16 hrs after the first OVA inhalation (green bars, short Challenge), 48 hrs after 3 daily exposures to OVA (blue bars, Standard Challenge) or 16 hrs after a single inhalation of OVA one month after the original challenge (red bars, Recall Challenge). Control mice received i.p. sensitizations but control PBS inhalations (white bars). Following a single exposure to inhaled OVA, methacholine produced a response dominated by an increase in Rn. In contrast, after 3 exposures to OVA the methacholine response was dominated by H and G. After a single recall challenge, the response to methacholine was entirely dominated by increases in G and H. **p<0.01, ****p<0.0001.