When spermicide comes in contact with sperm, it kills the sperm before they can enter the uterus and migrate to the fallopian tubes to fertilize the egg. Spermicides also kill some germs, such as gonorrhea. The most well known chemical spermicide is nonoxynol-9. Octoxynol is another. Spermicides come in various forms including jellies, creams, foams, suppositories, tablets and soluble films.
Foams come in aerosol containers with an applicator to insert the product into the vagina.
The sheets are folded and inserted into the vagina. How well spermicides prevent pregnancy is highly variable depending on whether they are used correctly and consistently. Their effectiveness also depends upon whether they are used in addition to another barrier method, such as the diaphragm, cervical cap, or condom. Spermicides can cause rash, irritation, or a burning sensation in either partner. Whether they decrease a woman's risk of becoming infected with HIV is unclear.