New research has found that some lubricants used in anal or vaginal sex can cause damage to those tissues that can leave people more vulnerable to sexually transmitted infections, including HIV.

Surprisingly, this is the first time that anyone has even looked at the question of whether basic sexual lubricants can cause damage to rectal tissue. The studies were presented at the Microbicides 2010 conference in Pittsburgh at the end of May.

A decade ago research presented at the first microbicides conference showed that nonoxynol-9 (N-9), a spermicide added to many lubricants to prevent contraception, was extremely toxic to rectal tissue. Later studies demonstrated that it increased the risk of becoming infected with HIV through vaginal sex.

The gay community learned to avoid lubes containing N-9, and pressured manufacturers to remove it from most products.

This long overdue study of the lubes themselves put six of the most commonly used products to a series of tests used to evaluate the toxicity of potential microbicides – products that might protect against HIV and other sexually transmitted diseases.

An online survey by International Rectal Microbicides Advocates identified the most popular lubes from among more than 150 brands and variations on the market.

It turned out that the most important factor is the osmolality, the amount of salts in the product.

Water-based lubes that were hyperosmolar "were actually damaging the epithelium of the rectal and cervical tissue," said Charlene Duzzetti, the University of Pittsburgh researcher who led the study. "The one that was not hyperosmolar, that didn't have any salts in it, and the silicon-based one, did not show any damage."

The top layer of cells that provides the greatest barrier protection from disease was stripped away by the lubes. The higher the osmolality of the lube, the greater the damage; but the damage was not as severe as what had been seen in tests of products using N-9.

Water-based lubes that scored poorly were Astroglide, Elbow Grease, ID Glide, and KY Jelly. The only water-based lube that scored well, with no harm to tissue, was PRe. The condom-friendly silicon-based Wet Platinum scored equally well.

The openly gay founder of Wet Lubricants said he was not surprised his product did well in the study.

"According to the study, ingredients in some of the lubricants tested were found to be responsible for stripping away cells on the rectal tissue, thus increasing the risk of transmitting disease," Michael Trygstad, founder and CEO of Trigg Laboratories, said in a statement. "The subject of the research study, the Wet Platinum product we market, does not contain these dissolved salts or sugars and was found by the study to have no toxicity."

A separate study, by UCLA researcher Pamina M. Gorbach, analyzed a group of 229 men who had engaged in receptive anal intercourse (RAI) within the last month, and 192 women who had done so within the last year. It asked about sexual behavior and tested them for chlamydia and gonorrhea.

It found that 76 percent used water-based, 28 percent used silicon-based, and 17 percent used oil-based [Crisco] lubricants, often in combination.

The men and women who used lube at the last recorded RAI were about twice as likely to have chlamydia or gonorrhea as those who did not use lube.

"This suggests that the use of some rectal lubricant products may increase the risk of STIs," Gorbach said.

Unfortunately, the sample was not large enough to see if there were any differences between the types of products used.

IRMA's chairman, Chicago AIDS Advocate Jim Pickett, said it's known that "dry" sex, with no lube, often results in great physical damage to the rectum. It may be more harmful than using even the most damaging lube. He called for more research and urged the gay community to become wise consumers when it comes to purchasing lube, just as they did in shunning products containing N-9.

Duzzetti suggested looking for lubes labeled isotonic or isosmolar, or silicon-based and condom compatible.

The silver lining in this research is that products behaved pretty much the same in both vaginal and rectal tissue samples. It suggests that a product that is safe in the vagina will be safe in the rectum. This may simplify the process of developing a microbicide that protects against HIV infection.

Bob Roehr is a biomedical writer with a focus on HIV and infectious disease. The article was first published in the Bay Area Reporter, San Francisco's oldest and largest local LGBT newspaper; and is republished with the author's permission.