Spermicide is a chemical that kills sperm. This prevents fertilization of an egg. Spermicide comes on most condoms (be sure to check the package), but are also marketed in forms that are inserted into the vagina. These include suppositories, foams, creams, inserts, film and gels. People can use a spermicide alone but it’s more effective at preventing pregnancy when used with a condom or diaphragm.

To use spermicides in the vagina, there is a slight waiting period before they are effective. Usually this time period is between 15 and 30 minutes. This allows time for body heat to melt the spermicide so it effectively covers the cervix.

When used alone and perfectly (every time you have vaginal sex), spermicides prevent pregnancy about 82 percent of the time. With more typical use that includes mistakes or misuse, they prevent pregnancy about 70 to 75 percent of the time. Condoms improve the chance of preventing pregnancy and infection. Together they can prevent pregnancy 97 percent of the time—a much safer rate.

Some people can be allergic to the chemicals used in spermicides. Soreness, itching, redness and swelling are the most common allergy symptoms. If someone has a reaction to the spermicides and has unprotected sex with a partner, then the rubbing against the irritated skin can make them more open to contracting an STD if their partner has one. This is another reason why using condoms with spermicides is a good idea.

Spermicides are sold in many drugstores and pharmacies, as well as online and in family planning clinics. One tube of gel or cream typically costs about eight dollars. One dose of an insert, film or foam typically costs about a dollar and is sold in packs of three, six or more.

For more information and photos of all the birth control methods, go to the story “An A to Z of Contraception” by Claire Marchetta, 18, Staff Writer.