Recurrent vaginal candidiasis is a worldwide problem affecting millions of women. Candida albicans is a potent allergen in some situations and it has been suggested that local hypersensitivity to this yeast can be a factor in the prolongation of the disease. A small number of studies show some benefits of allergen immunotherapy in these patients. We evaluated the efficacy of C. albicans allergen immunotherapy in women with immediate skin test positive for this fungus. We conducted a prospective cohort study of women with recurrent vaginal candidiasis referred by gynecologists to an allergist. All patients had established positive C. albicans in vaginal cultures and were unresponsive to other modes of treatment. None had diabetes or AIDS. In their allergy evaluation, they had an immediate (prick or intradermal) skin test positive to C. albicans. These women were offered the option of C. albicans allergen immunotherapy for a period of 24 months. The efficacy of therapy was evaluated by comparison of the mean incidence of episodes per year before and after immunotherapy Over a period of 33 months, 34 women were enrolled (mean age 33.5 years; range 18-57). They were treated with weekly injections of C. albicans allergenic extract over a mean (+/- SD) period of 17.4+/-7.2 months (4-24 months). Twenty-two of the women had improvement in symptoms. There were complete responses, i.e., absence of acute episodes for 2 years, in nine patients (26%) and partial responses, i.e., decrease in the number and intensity of episodes, in 13 patients (38%). Overall there was a 64% improvement in these patients (95% CI: 46.5-79.9). Eleven patients showed no improvement and one worsened. The effects were evident after 2-12 months of therapy (mean 3.5 months). The mean incidence of episodes of vaginitis per year decreased from a mean (+/- SD) of 8.5+/-2.6 to 3.6+/-4.3 (p = 0.000). The study also showed that the majority of patients were atopic (70%), had allergic rhinitis (67%) and familial history of allergy (70%). Our results suggest that in a subgroup of patients with recurrent vaginal candidiasis, C. albicans allergen immunotherapy lowers the number and intensity of episodes.