Treatment of recurrent herpes simplex labialis with levamisole.

Because deficient immune responses may play a contributory role in recurrent herpes simplex labialis, an immunomodulating agent, levamisole, has been advocated for therapy. Forty-two patients with a high frequency of recurrent herpes simplex labialis were followed for a mean of 7.8 months (range 4 to 12) and treated for 3 days at the onset of each episode of herpes with one of three different doses of levamisole or placebo in a randomized, double-blind study. Statistical analysis revealed that as the dosage increased, so did the frequency of recurrences (P = 0.007). Conversely, duration of the lesions and lesion pain decreased with increasing dosage (P = 0.05 and 0.03). These results indicate that levamisole is not an appropriate drug for the management of recurrent herpes simplex labialis. The paradoxical response to an immunomodulator (increased frequency, decreased severity) provides evidence that altered host responses may contribute to the pathogenesis of the disease.