They come ribbed, flavored and multicolored, in lambskin or latex. People alternately despise, obsess over or refuse to use them.

Despite the variations, there are some constants to condoms: They protect against pregnancy and sexually transmitted disease. You can feel and see them. And it's up to men to wear them. 

Not so anymore. Drug stores in both Canada and the United States will soon carry a new condom for women — one that's invisible to the naked eye, and the just plain naked. 

Researchers at Laval University in Quebec City have received $235,000 from the Canadian federal government to begin testing the Invisible Condom on women this fall. 

The substance, a liquid at room temperature that becomes a gel when warmed by body heat, has the same purpose as a standard condom. The Invisible Condom is applied intravaginally and also acts as a chemical barrier, according to project researcher Dr. Andre Desormeaux. 

 
'There is no other alternative for women to protect against STDs' — 
Dr. Andre 
Desormeaux 
 

Fifty Canadian women will be the first to try the product in tests measuring the substance's toxicity and safety in humans. Subsequent phases will study its effectiveness against HIV, herpes, other STDs and pregnancy. 

Desormeaux predicts the Invisible Condom will be marketed within two years, first in Canada and later in the United States, Europe and elsewhere around the world. 

Closer to home, a biotech company called Procept Inc. in Cambridge, Mass., has nearly completed the first phase of human research with a similar product: PRO 2000, a topical vaginal gel that prevents the transmission of HIV, herpes, chlamydia and other such diseases. 

Like the Invisible Condom, PRO 2000 contains microbicides, which block viruses from entering cells. 

"Clearly, women throughout the world are increasing their risks for sexually transmitted infections," said Albert Profy, Procept's vice president of research and development. He pointed to statistics showing that heterosexual transmission of HIV is the fastest-growing type of transmission in the U.S. 

In this erogenous age, experts say many women could use a little bedroom magic. 

Desormeaux pointed out women's only alternative thus far has been the Reality female condom, which he said is not very popular. 

"It is very huge," he said. "It doesn't stay in place — it's like a plastic bag. I don't think women like putting this in the vagina." 

O.B. Parrish, chairman of Reality manufacturer the Female Health Company, said Reality is "Well-accepted. There are certain people who don't like it, but the majority of people like it — both women and men." 

Still, experts say, women would benefit from having more and better options. 

"These types of products would offer women a method they can use, maybe even covertly," Profy said. "Male condoms work very well, but men will sometimes refuse to use them. Nobody really likes condoms." 

The Invisible Condom and PRO 2000 have been shown to prevent pregnancy in rabbits — no small feat considering their reproductive reputation. More importantly, it's a good indicator the gels will be effective birth control for people. 

The Canadian and American products work somewhat differently, though both can be applied anytime from a few hours to immediately before intercourse. 

The Invisible Condom's initial liquid form allows the chemicals to seep more deeply into the cells. At body temperature, the substance turns into a gel, physically and chemically blocking viruses. It leaves the system through vaginal secretion over an estimated period of 2 to 6 hours. 

PRO 2000 stays in its gel form and chemically prevents viruses from entering human cells, according to Profy. Though it doesn't kill sperm, it is believed to stop fertilization by stubbornly binding to their heads — meaning the determined little swimmers can't attach to the egg. 

Procept, which began developing the product in 1994, is three-quarters of the way through the phase-one studies testing its safety for humans, Profy said. The National Institute of Health's allergy and infectious diseases division is funding the clinical research. 

Profy predicts the day will soon come when lab mice and rabbits won't be the only ones reaping the benefits of the clear female condoms researchers like him are busy perfecting. 

He expects his cutting-edge compound to be marketed to American women in about five years. He hopes to eventually sell it over the counter. 

"We've shown it works on animals," he said. "The challenge is to show it works on humans."