The objective of this study is to determine the magnitude and duration of the reduction in pH (acidification) following a single dose of Acidform vaginal gel containing 3, 4, or 5 g compared with hydroxyethylcellulose placebo gel (4 g) or no treatment. Vaginal pH will be measured 1 h, 6 h, 12 h, 24 h, then once daily for 7 days. In addition, the participants will be assessed for an exploratory endpoint to the determine effect of one dose of Acidform gel (3, 4 or 5 g) or placebo gel (4 g) or no treatment, on asymptomatic bacterial vaginosis (BV).