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The Hidden Dangers of Nonoxynol-9

The Spermicide Can Actually Increase Your Risk of STDs


Updated April 28, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Many people think that if a little bit of spermicide is good, than a lot of spermicide is bound to be better. But that theory is bound to backfire, because many spermicides, when used in excess, can actually increase your risk of getting or giving a sexually transmitted disease (STD).

What is a Spermicide?

A spermicide is any compound used to kill sperm. Spermicides are used in many contraceptives, and they come in several forms. Contraceptive foams, creams, suppositories, and films all contain spermicides, and spermicides are also needed for diaphragms and cervical caps to be effective. Most spermicides currently available in the United States contain nonoxynol-9 (N-9), which is also the spermicide in the Today sponge. Other spermicides, and spermicidal microbicides, are currently under development, and many are designed to avoid the problems currently being seen with N-9 use.

What is Nonoxynol-9 (N-9)

Nonoxynol-9 is basically a type of detergent. It disrupts the plasma membranes (outer barrier) of sperm and other cells and has been shown in the laboratory to be quite effective at killing many STD pathogens including HIV, herpes, chlamydia, and gonorrhea. Other commercial spermicides that contain oxtoxynol-9 are also detergents and have similar properties to nonoxynol-9.

Why is Nonoxynol-9 Problematic?

When used in high dosages, or when used frequently, N-9 causes two types of damage to the vaginal epithelium (layers of skin cells.) It causes inflammation of the vagina and cervix, and it can actually kill off layers of cells. Both of these actions render a woman more susceptible to infection by various sexually transmitted diseases. They may also make it easier for her to transmit STDs to her partner.

Regular use of N-9 may increase a person's risk of HIV, herpes, and other sexually transmitted diseases. It may not even require frequent use for problems to be seen. At least one study done in mice has shown that just one vaginal dose of N-9 can increase susceptibility to herpes infection.

What Should I Do?

  • Consider using non-lubricated condoms with your own N-9-free lubricant, or non-spermicidal condoms, particularly if you have sexual intercourse more than once or twice a day.
  • Talk to your doctor about possible alternative forms of contraception if you are using a diaphragm, cervical cap, or the Today sponge, and you are at risk of sexually transmitted infections.

Hillier S. et al. "In Vitro and In Vivo: The Story of Nonoxynol-9." 2005. JAIDS: 39(1):1-8.
Gupta, G. "Microbicidal spermicide or spermicidal microbicide?" 2005. Eur J Contr Repro Health Care: 10(4):212–218.
Cone, R.A. et al. "Vaginal microbicides: detecting toxicities in vivo that paradoxically increase pathogen transmission" 2006. BMC Infectious Diseases: 6:90

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