The antifungal activity of scallop-shell powder heated at 1000 degrees C for 1 h against Trichophyton was kinetically investigated and the possibility of applying the powder to the treatment of dermatophytosis was examined. The death rate of T. mentagrophytes NBRC5466 in the heated shell powder slurry increased with powder concentration, following first-order reaction kinetics. Elevated slurry temperatures increased both the apparent first-order death rate constant (k) and the dilution coefficient (n) representing the dependence of k on reagent concentration. The activation energy for the death of NBRC5466 was almost equal to that for bacteria, whereas the n value was much smaller than that for bacteria. In addition, the trial using heated shell powder treatment on feet showed the possibility of its application to treat dermatophytosis.