Using Spermicides
Spermicides can increase the effectiveness of barrier methods of contraception, but they do not provide reliable contraception when used alone. As with all types of contraception, it is important to insert or apply the spermicide in exactly the right manner in order for it to work properly. Spermicide must be used every time you have vaginal sex. If you have sex multiple times during a time frame, it is necessary to reapply the spermicide each time before you have sex.
Side Effects
Although spermicide is fairly easy to obtain and use, it is not a perfect method. Spermicides have been found to increase a woman’s risk for urinary tract infections. Some women (and men) have experienced irritation and allergic reactions using spermicides. Irritation from spermicides can also increase risk of sexually transmitted diseases, including HIV.
Effectiveness
Spermicides have a fairly high rate of failure, ranging from 5% to 20%. However, when used correctly and consistently (every time you have sex) in combination with other forms of birth control such as the diaphragm or cervical cap, spermicides are highly effective.