The use of recombinant human interferon alpha subtype D (RIFNαD) was effective in reducing shedding of herpes simplex virus type-1 induced by iontophoresis of 6-hydroxydopamine and epinephrine. A post stimulation treatment schedule of RIFNαD, one drop four times a day was as effective as pre-treatment, using the same dose regimen. The levels of interferon (IFN) present in the assay system are not sufficient to produce an antiviral effect. The levels of IFN required to suppress cell growth are substantially higher than the concentrations detected in the assay system.