Antimicrobial and contraceptive compositions and methods which prevent and / or reduce the risk of transmission of sexually transmitted diseases through sexual activity as well as prevent and / or reduce the risk of 
pregnancy are provided. The compositions contain (1) a matrix-forming agent, (2) a bio-
adhesive agent, (3) a 
buffering agent, (4) optionally a 
humectant, (5) optionally a 
preservative, and (6) water; wherein the composition is suitable for application within the 
vagina; wherein the compositions form a semisolid matrix on contact with ejaculate (thereby 
trapping ejaculated microbes and spermatozoa); wherein the composition causes hardening of 
cervical mucus (thereby decreasing the probability of 
sperm entry); wherein the composition forms a bio-
adhesive layer over vaginal surfaces (thereby preventing or reducing the risk of contact of STD-causing microbes with the vaginal surfaces); wherein the composition maintains an acidic vaginal pH of less than about 5 in the presence of 
semen ejaculated from the male; and wherein the composition does not significantly impair the natural microbiological balance within the 
vagina. The 
antimicrobial and contraceptive compositions may also contain additional 
antimicrobial and / or contraceptive agents (e.g., nonoxynol-9, octoxynol-9, 
benzalkonium chloride, phosphorylated hesperidins, sulfonated hesperidins, 
polystyrene sulfonates, substituted 
benzenesulfonic acid formaldehyde co-polymers, H2SO4-modified mandelic acids, povidone 
iodine, 
itraconazole, 
ketoconazole, 
metronidazole, 
clotrimazole, 
fluconazole, teraconazole, 
miconazole, 
tinidazole, iconazole, 
chloramphenicol, 
nystatin, cyclopiroxolamine, and the like).