Suzi Godson

Oral sex is not a risk-free activity, but then neither is crossing the road. Risk is relative. If you wait until the little man turns green and look left and right, you have a relatively good chance of getting to the other side. Conversely, if you orally pleasure a different lover every night, you run a relatively high risk of acquiring a sexually transmitted infection.

Pedestrians crossing the road simply want to get to the other side, but those engaging in oral sex rarely stop when they get there. This makes it difficult to isolate and quantify the “actual” risk associated with oral sex. To establish whether an infection can be transmitted orally, scientists differentiate between “documented risk” (incidences where an STI has been proved to have been transmitted orally), and “theoretical risk” (risk that is possible but has never been scientifically documented). With HIV, for example, there is both theoretical and documented risk of transmission as a result of fellatio, cunnilingus and analingus, but the documented risk for these practices is substantially smaller than it is for vaginal and anal penetration.

Gonorrhea survives well in the throat, so throat infections from oral sex are relatively common. I know one girl who got it in her eye, which was deeply unpleasant. Oral sex is also an efficient way to transmit syphilis. For the full stomach-churning lowdown, there is a chart of all the infections that are known to spread through oral sex on the San Francisco City Clinic website (dph.sf.ca.us/sfcityclinic/stdbasics/stdchart.asp). It lists the “known” risks for performing unprotected oral sex on a man as chlamydia, gonorrhea, hepatitis A*, herpes (rare), HPV (warts), shigella and syphilis. The “possible” risks are hepatitis B and HIV. And the unknown risk is hepatitis C.

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BACKGROUND

• My boyfriend wants doggy style sex in front of a mirror

• I'm turned on by my wife breastfeeding

• I eye up women when my wife isn't around

• Should my boyfriend be screened for sexual health?

• Is my friend a nymphomaniac?

Performing and receiving oral sex on a woman is far less dangerous. The clinic lists herpes as the only “known” risk, but bear in mind how widespread the virus is. HPV is considered an “unknown” risk as there is no documented evidence that it is transmitted through oral sex. However, the HPV virus is shed from the surface of warts, which makes it a theoretical risk. And research at the College of Malmö, in Sweden, has established a clear link between HPV and oral cancer. People who have one to five oral sex partners in their lifetime double their risk of throat cancer, while those who have more than five oral-sex partners have a 250 per cent increased risk.

So, if you're having sex with a crusty lothario, a “barrier method” is the only way of ensuring that you are protected. Non-porous clingfilm probably serves, but condoms and dental dams (a thin latex sheet that can be placed over the genitals), are the more obvious choice. However, sucking on a cola-flavoured condom is only one step up from snogging with a mouthful of clingfilm.

As for sticking a square of latex over your lady bits before they are kissed goodnight? That's an indignity best avoided by getting a clean double bill of sexual health before swapping bodily fluids with anyone.

Suzi Godson is the author of The Sex Book (Cassell, £16.99) and The Body Bible (Penguin, £16.99)

Dr Thomas Stuttaford

The surfaces of the body vary and provide as many snug nurseries for micro-organisms as the greenhouses at Kew do for exotic plants. The lining of the mouth, eyelids, genitalia and peri-anal area all have similar structures microscopically and, therefore, provide equally good environments for the bacteria and viruses that cause sexually transmitted diseases. Oral sex is, therefore, almost as risky as genital intercourse, though clingfilm seems a rather unromantic and drastic solution.

There are other factors as well as the structure of the mucous membranes lining the mouth and other sites that may determine whether infection occurs. The bacterial or viral loads, which is the concentration of organisms in the infecting partner's fluid, and the immune response of the recipient to the bacteria, are also important. Another factor is where the bacteria are deposited. A blob of sperm on a cheek will be brushed away and is unlikely to transmit disease, but a blob of sperm in the vulva can stay there for hours and has a much higher chance of becoming established. Cosy, undisturbed but oxygenated areas are optimum for the development of bacteria.

It is hard to understand why there was such initial reluctance from the Department of Health and other interested medical and social organisations to accept that HIV, for example, could be spread by both men and women and that its transmission was not confined to homosexual men having anal intercourse. It took years for many medical authorities to accept that men could catch HIV from women, as well as other men, and that it was present in other fluids as well as blood and semen. It took even longer for them to accept that HIV could be transmitted by oral sex, but Swedish research - and now that in other countries - has shown that in an appreciable percentage of cases the virus could have been passed on only orally.

In any reputable genitourinary clinic it is standard practice to examine the throats of patients who have consulted the doctors because a man has noticed a urethral or penile discharge, or similarly if a woman has vaginal or urethral problems. I was consulted during my days in general practice by several patients who had a chronic sore throat that had defied standard treatment. The answer lay below the belt; they had gonococcal infections in the throat, and had been having both oral and genital sex.

Gonorrhoea and HIV are not the only infections that can be spread by oral sex. Chlamydia may also be; syphilis can be spread orally, and herpes is regularly passed on in this way, as are warts occasionally - and it is strongly suspected that some of these warts are of the strains that transmit cancer. This may be a factor in the recent increase in the number of malignancies diagnosed in the mouth and throat.

Rather than resorting to clingfilm, it would be better if you and any new regular partner had tests at a good clinic. Condoms will offer protection to a varying degree against sexually transmitted diseases. Abstinence and fidelity are the only truly adequate protection, but it is unrealistic to expect that everyone will want, or accept, this advice.

Dr Thomas Stuttaford, the Times doctor, spent many years working in a genitourinary clinic

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