A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Can HIV pass through the pores in latex condoms?

May 6, 1994

Dear Cecil:

Get a load of this clip from the Washington Times. It says the latex used in condoms contains pores through which HIV, the AIDS virus, can readily pass — suggesting that "safe sex" using a condom may not be very safe. What gives? Answer quickly. Lives are in the balance!

Cecil replies:

I'll say. Your clip is a 1992 letter to the editor from Mike Roland, editor of Rubber Chemistry and Technology, a publication of the American Chemical Society. Roland argued that "the rubber comprising latex condoms has intrinsic voids [pores] about 5 microns (0.00002 inches) in size. Since this is roughly 10 times smaller than sperm, the latter are effectively blocked.... Contrarily, the AIDS virus is only 0.1 micron (4 millionths of an inch) in size. Since this is a factor of 50 smaller than the voids inherent in rubber, the virus can readily pass through."

This sounds scary, but there are a couple problems with it. First, Roland bases his statement about a 5 micron latex pore size on a study of rubber gloves, not condoms. The U.S. Public Health Service says that condoms are manufactured to higher standards than gloves. Condoms are dipped in the latex twice, gloves only once. If just 4 out of 1,000 condoms fail the leak test, the whole batch is rejected; the standard for gloves is 40 out of 1,000. A study of latex condoms by the National Institutes of Health using an electron microscope found no holes at a magnification of 2000.

The second problem with Roland's letter is that it suggests, at least to the casual reader, that condoms offer no protection at all against HIV. That's not so. Roland himself estimates that condoms reduce HIV transmission risk by a factor of three. He cites a 1993 analysis by S. C. Weller suggesting that condoms are 69 percent effective in preventing HIV transmission.

The government's counterargument to this is that Weller did not distinguish between consistent and inconsistent users of condoms. Government spokesmen cite two European studies of "serodiscordant" heterosexual couples — that is, one partner had HIV, the other didn't. One study found that among couples using condoms consistently, there were zero cases of HIV transmission between the partners. Inconsistent users had a 10 percent infection rate. The other study found an infection rate of 1.1 percent between consistent users, 5.7 percent between nonusers. In other words, conservatively speaking, condoms reduced HIV transmission risk by a factor of 5.

We could argue about these numbers, but let's put this in perspective. Roland thinks condoms reduce AIDS risk by a factor of 3. A study cited by the government says they reduce it by a factor of 5. Avoiding high-risk sex partners, it's believed, reduces it by a factor of 5,000.

In short, regardless of who's right about latex, you'd be foolish to make condoms your only defense against infection. Abstinence or, more realistically, avoidance of high-risk sex partners are far more effective strategies. (If you're a gay male and thus in a high-risk group to start with, at least stay away from IV drug users.) On the other hand, condoms do offer substantial protection, and if you insist on having sex with a high-risk partner, they're a lot better than no protection at all.

Condoms versus AIDS, round 2

Dear Cecil:

Thanks for nothing, Cecil. At first your column on condoms seemed long overdue: a concise rebuttal to the Christian right's disinformation campaign about how HIV supposedly can readily pass through "pores" in latex condoms. Too bad it took you only a few paragraphs to lapse into the kind of tired, false propaganda about "abstinence" and "high-risk partners" that would fit quite comfortably alongside the vitriolic bigotry in the pages of the Washington Times.

You point out that the 5-micron "intrinsic pores" scare is based on the latex in rubber gloves, not condoms, and you point out the vast differences in manufacture of the two. Good. You cite studies about correct, consistent use of condoms, a distinction the anti-condom, anti-sex troops never make while making the rounds of talk shows. Fine.

But why skip the biggest hole in the "porous latex theory"? HIV isn't some free-ranging microscopic bug; it's an intracellular virus, and it's these cells that would somehow have to squeeze through those fabled 5-micron holes.

And then, for you, it's back to the same old idea that "only bad people get AIDS"; and for the self-satisfied schmucks behind Cecil Adams, bad people are evidently those who have sex outside the confines of a heterosexual monogamous marriage contract. "If you're a gay male and in a high-risk group to start with, at least stay away from IV drug users"?! It must be quite reassuring to think of all queer men as inherently diseased and of all drug users as inherently self-destructive. Too bad that's a crock. The queer men who have made safe sex a consistent part of their sexual lives and the IV drug users who make a point of cleaning and not sharing their works are exercising a hell of a lot more self-restraint and self-protection than the idiots who think they're immune because they're not in a high-risk group. I guess it's called the Straight Dope for a reason: it's heterosexist … and stupid.

Cecil replies:

Great letter, P. In more than 20 years of writing this column it's the first defense I've gotten of IV drug use, which to be honest I do think of as "inherently self-destructive." But I didn't say "queer men" were "inherently diseased." I said they were in a high-risk group, which no one disputes, and that while condoms significantly reduce the risk of infection, no one should think they will render you immune to AIDS. Discretion in your choice of sexual partners is a sound strategy regardless of your sexual orientation. That said, by all means use condoms as well.

As for the substantive issue you raise, it's true "the transmission of HIV by genital fluids most probably occurs through virus-infected cells since they can be present in larger numbers than free virus in the body fluids" (Jay Levy, "Pathogenesis of Human Immunodeficiency Virus Infection," Microbiological Reviews, March 1993 — an exhaustive treatment of the subject). But it would be wrong to construe this to mean that HIV is transmitted only by cells. When I spoke to Dr. Levy he readily conceded that HIV may be transmitted by free virus as well. He did add that the viscosity of semen may hinder the passage of such virus through the latex barrier.

We could debate the technical stuff all day. My point is this: for whatever reason — pores, improper use, etc. — real-world research shows condoms don't offer 100 percent protection against AIDS. Maybe not, say the AIDS experts, but if you tell people that they'll use it as an excuse not to use condoms. To which I reply: the arguably greater danger is that they'll use condoms the way some weight watchers use Diet Coke — as an excuse to continue dangerous behavior (e.g., promiscuous sex, not gay sex per se). If that's "anti-eros," as some people seem to think, too bad. A friend of mine who died of AIDS attributed his illness to a wild weekend he'd once had. It's hardly anti-sex to wish he'd stayed home.

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