Another P.S. on polyurethane condums. Yes, they do NOT have pores - but the FDA has not allowed any manufacturers to make claims about the prevention STDs - although common sense would assume they are much much safer. Studies still need to be conducted.
http://www.postgradmed.com/issues/2000/04_00/pn_condoms.htm
Latex condoms are the only ones known for sure to prevent transmission of HIV. Newer, soft plastic (polyurethane) condoms may also be effective, but we do not yet have enough information to recommend them. However, they are an important option for people who are allergic to latex. Plastic condoms do not fit as well as the more flexible latex devices, and they may slip off during use.
Lambskin condoms are quite porous and do not protect against HIV. They block the flow of sperm but not the spread of viruses. Novelty condoms, such as those with extra "nubbies" or "hot" designs, often do not protect as well as standard latex condoms against STDs. Check the label on the package.
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Another link for the below information:
http://www.aegis.com/pubs/cdchotb/1995/CDC00115.html
Centers for Disease Control and Prevention
These are answers from the Centers for Disease Control and Prevention (CDC) to questions submitted by the CDC National AIDS Hotline concerning polyurethane condoms.
1. Is the use of polyurethane condoms recommended by CDC?
The FDA has approved the male polyurethane condom for sale in the United States, but has not allowed the manufacturer to make any claims about the prevention of pregnancy or STDs until ongoing studies are completed. Laboratory testing has shown that particles even as small as sperm and viruses like HIV cannot pass through this polyurethane material. An actual "recommendation" by CDC has not been made yet.
2. Latex condoms are regulated in the United States and must meet FDA standards. What kind of standards will polyurethane condoms need to meet?
Standards are currently being developed.
3. Are there microscopic holes or pores in polyurethane? How are we sure that polyurethane pores are small enough to keep HIV out?
There are no pores or holes in polyurethane.
4. Is there any information on reliability rates?
Laboratory testing has shown that particles, even ones as small as sperm and viruses like HIV, cannot pass through this polyurethane material. However, the manufacturer has not completed the clinical trials necessary to prove protection against pregnancy, HIV, and other STD's. Studies are now underway.