Getting HIV from Oral Sex
What you need to know:
It is possible but extremely rare. The risk is much lower than anal or vaginal sex.
Scientific Data on HIV transmission in Oral Sex is not strong. The type of Oral Sex that carries the highest risk is Receptive Fellatio. Ejaculation, Gum Disease, Poor Dental Hygiene, Ulcers in the mouth and the presence of blood can increase the risk.
Oral sex refers to contact of the mouth to the ano-genital region.
While every one of these oral sex acts have case reports suggesting that they are possible, the only one with enough evidence to estimate a risk is Receptive Fellatio.
Therefore, it is accepted by most experts that this is the highest risk of all sex acts. What exactly is the risk of contracting HIV from Oral Sex?
Unfortunately, no one knows for sure. Most experts would agree that risks are extremely low.
Factors that increase the risk of transmission are:
There have been many studies done on the transmission of HIV in oral sex. The vast majority concluded that oral sex in itself is NOT a risk factor for HIV transmission.
There were however a handful of studies that found oral sex to be significantly associated with HIV infection. These studies focus on MSM (men-who-have-sex-with-men), CSWs (commercial sex workers) and people from lower socio-economic groups with a higher incidence of poor oral hygiene and mouth sores.
What serves for more scary reading are the case reports. Bear in mind that case reports are not as scientifically or statistically significant or important as clinical studies.
That said, there have been many case reports on possible Oral transmission of HIV. More notable cases include:
Studies conducted in San Francisco and London in 2000 and 2001 amongst MSM indicated that 6% to 8% of HIV +ve cases were believed to be cause by oral sex. Note that this does NOT mean the risk of getting HIV from oral sex is 6% to 8%.
So what exactly is the risk of getting HIV from oral sex?
No one really knows. A systematic review done in 2008 concluded that there was insufficient data to precisely estimate the risk. In my opinion, there are so many variable factors that there is really no way to accurately estimate the risk anyway.
However, everyone would agree that the risk is less than penetrative sex which has been estimated to be anywhere between 1% and 0.01%. So what we can say at this point in time is that the risk of contracting HIV via oral sex is less than this.
The only type of oral sex where there was any kind of risk estimation at all was receptive fellatio (the partner using his mouth) amongst MSM. The magic number given to this per-act-risk is 0.04%. Even then, some experts believe that this risk was over estimated because it was calculated from very complex mathematical models.
What is in saliva that kills HIV?
In 2008, a Swedish research team discovered that HIV –ve people produced antibodies in their saliva that can ‘kill’ the HIV virus. This provided an explanation as to why HIV transmission via oral sex is so low.
Another study found that the concentration of saliva is so low (i.e. hypotonic) that it ‘kills’ the white blood cells that carry the HIV virus. There was an experiment done in the lab (not on live patients) to show that if the volume of semen is high enough, it makes the overall environment closer to the concentration of cells (i.e. isotonic) and therefore increases the chance of cell survival and as a result increases the risk of HIV infection. This may explain why ejaculation is thought to increase HIV risk in oral sex.
There was also a study that suggested that a chemical found in saliva called Mucin can also inactivate the HIV virus.
The real problem is that there have not been any good quality studies on HIV and Oral Sex. Most are based on interviewing HIV +ve patients on their sexual practices. So there is a problem of ‘recall bias’ (i.e. they forgot or their lying).
Furthermore, most studies involve relatively few participants. Since the incidence of HIV from oral sex is so low in the first place, many studies did not even have a single case of HIV transmission so were unable to estimate the risk in anyway.
So far in the studies that have been done, the estimated risk of contracting HIV from oral sex is either zero or really close to zero. So close to zero that physicians like myself find it hard to counsel patients who are concerned about getting HIV from oral sex. On the one hand, we do not want to tell them with absolute certainty that they are not at risk, on the other hand, we do not want to unnecessarily play up the risk leading to unwarranted anxieties, tests and treatments.