They come as creams, films, foams, gels, or suppositories, which you insert deep inside your vagina.
They work by stopping the sperm from moving, so they can’t swim up through the cervix to fertilise an egg.
Spermicides don’t work very well on their own. They’re usually used to back up another birth control method, like a cap, diaphragm, or condom.
Condoms with spermicide
Spermicide-lubricated condoms contain a chemical called nonoxynol-9. This kills sperm – or at least, it stops them moving.
Some people who use condoms lubricated with spermicide find they cause redness, itching, or irritation. Women are more likely to get side effects from spermicide. It can also make them more likely to get urinary tract infections.
If your only option is to use a lubricated condom or not to use a condom at all, it’s still much safer to use the condom.