Disease control tools are needed to mitigate the effect of the fungal pathogen Batrachochytrium dendrobatidis (Bd) on amphibian biodiversity loss. In previous experiments, Bd metabolites (i.e., noninfectious chemicals released by Bd) have been shown to induce partial resistance to Bd when administered before live pathogen exposure and therefore have potential as an intervention strategy to curb Bd outbreaks. In the wild, however, amphibians inhabiting Bd-endemic ecosystems may have already been exposed to or infected with Bd before metabolite administration. It is therefore critical to evaluate the efficacy and safety of Bd metabolites applied postexposure to live Bd. We tested whether Bd metabolites administered postexposure would induce resistance, exacerbate infections, or have no effect. The results confirmed that Bd metabolites applied before pathogen exposure significantly reduced infection intensity, but Bd metabolites applied after pathogen exposure neither protected against nor exacerbated infections. These results reveal the importance of timing the application of Bd metabolites early in the transmission season for Bd-endemic ecosystems and emphasize that Bd metabolites prophylaxis may be a useful tool in captive reintroduction campaigns where Bd threatens the success of re-establishing endangered amphibian populations.