Difulcan is an oral antifungal drug that can be used for treating chronic vaginal yeast infections. Premarin is an estrogen drug used for treating vaginal dryness due to lack of estrogen during menopause. I am not sure why are you experiencing vaginal dryness. In your case, menopause is out of the question due to your age (late 20's). Acute yeast infections are usually treated with a local antimycotic. Chronic (reoccurring) vaginal infections are treated with local and systemic (oral) antimycotics. In case of chronic yeast infections, a microbiological examination should be completed to test yeast sensitivity to various antimycotics.