Published: 31 July 2009
  • Poppers (nitrite-based inhalants) more than double the receptive partner's risk of HIV infection during unprotected anal intercourse.
  • This may be because poppers increase blood flow to the rectal tissues, heightening their susceptibility to infection.
  • Most evidence suggests that poppers do not make unprotected anal intercourse (UAI) more likely, but that they increase the risk of HIV infection in men who are having UAI.
  • There is no clear evidence that the insertive partner's risk of infection is affected by poppers use.

Poppers are inhalable forms of butyl and other nitrites.1 2 3 They are widely used as a recreational drug among gay men in the UK, with some 40 to 50% or more reporting their use.4 Especially popular for use during receptive anal intercourse, sniffing poppers relaxes the anal sphincter muscles, making intercourse easier and intensifying pleasure.

However, using poppers during unprotected, receptive anal intercourse significantly increases the risk of HIV infection. A large UK case-control study, INSIGHT, found that, independently of other factors, use of poppers more than doubled the risk of seroconversion for men who had unprotected, receptive anal intercourse.5 (The increase in risk was even higher in the crude analysis, but after controlling for other factors, poppers increased the risk of infection by 2.4-fold.) These findings were the basis of a prevention education campaign aimed at gay men in the UK.

Several other North American studies6 7 8 9 10 11 have also found that, among men who have unprotected anal intercourse (UAI), the risk of seroconversion is roughly doubled in those who use poppers. The reasons for this increased risk are not completely understood. They are probably mainly physiological, but may include some behavioural factors as well.

Physiologically, inhaling poppers relaxes smooth muscle tissues. This includes the muscles not only of the rectum, but also of blood vessels, causing an abrupt drop in blood pressure and an increase in blood flow. This increased blood flow and expansion of blood vessels in the rectum may make the rectal tissues more susceptible to HIV infection.

There has been much debate over the years as to whether poppers interfere with immune function. In the early years of the epidemic, widespread poppers use among the earliest AIDS cases drove speculation that poppers contributed to, or even caused, the immune suppression culminating in AIDS. Isolated arguments to this effect persist to this day in 'AIDS dissident' sectors, but are almost universally dismissed.12 13 Some modest, short-term reductions in immune cells have been seen in animal and human studies. Overall, however, evidence that poppers cause any significant degree of immune suppression is sparse, and very little research on the subject is recent. It is an open question whether the increased risk of HIV infection due to poppers might be partially due to immune-suppressive effects.

On the behavioural side, it is possible that poppers may lead to reduced inhibitions and longer, rougher sex, making transmission more likely. Studies tend to show that poppers do not actually lead to abandoning condom use or other increases in risky sex, although this is not completely clear. The INSIGHT study did find that men who had unprotected, receptive anal sex were more than nine times more likely to do so with partners of known HIV-positive or unknown serostatus if they were using poppers. A recent US study9 found that HIV-positive men used poppers during UAI more than HIV-negative men. However, this does not mean that poppers caused the differences in behaviour: it may be that men who are already having UAI are also more likely to use poppers when they do so. Other studies have not found that poppers lead to an increase in unprotected sex.6 7

Much less is known about how poppers affect risk for the insertive partner in UAI. This actually involves two questions: the effect on risk if the insertive partner uses poppers himself, or if the receptive partner uses them. If poppers do in fact affect the rectal tissues so as to increase the receptive partner's risk, then it is at least plausible that this might place the insertive partner at greater risk if the receptive partner is HIV-positive. At present, however, this question does not appear to have been studied.

The INSIGHT study did not find that use of poppers by the insertive partner had any effect on risk. In the North American studies mentioned above, risk was not broken down by active/passive role, so it is not clear whether there is any difference or not.

Finally, poppers have been associated with increased risk of acquiring HHV-8, the virus associated with Kaposi's sarcoma. This is discussed in detail in NAM's HIV Treatments Directory.

Related Links


  1. Colfax G, Guzman R Club drugs and HIV infection: a review. Clin Infect Dis 42(10):1463-1469, 2006
  2. Dax EM Amyl nitrite alters in vitro human immune function. Immunopharm and Immunotox 13(4): 577-587, 1991
  3. Porter RS et al, ed. 'Volatile Nitrites.' The Merck Manual Online. www.merck.com/mmpe/sec15/ch198/ch198m.html#sec15-ch198-ch198m-400. Date accessed: 28 April, 2009
  4. Weatherburn P et al. Multiple chances: findings from the United Kingdom Gay Men's Sex Survey 2006. Sigma Research, 2008
  5. Macdonald N et al. Factors associated with HIV seroconversion in gay men in England at the start of the 21st century. Sex Transm Infect 84:8-13, 2008
  6. Buchbinder S et al. Sexual risk, nitrite inhalant use, and lack of circumcision associated with HIV seroconversion in men who have sex with men in the United States. J Acquir Immune Defic Syndr 39(1):82-89, 2005
  7. Lampinen TM et al. Nitrite inhalant use among young gay and bisexual men in Vancouver during a period of increasing HIV incidence. BMC Public Health. Published online 15th March, 2007
  8. Thiede H et al. Determinants of recent HIV infection among Seattle-Area men who have sex with men. Am J Public Health 99: S157-S164, 2009
  9. Carey JW et al. Drug use, high-risk sex behaviors, and increased risk for recent HIV infection among men who have sex with men in Chicago and Los Angeles. AIDS and Behavior (online edition), 2008
  10. Ostrow DG et al. Specific sex drug combinations contribute to the majority of recent HIV seroconversions among MSM in the MACS. J Acquir Immune Defic Syndr (online edition), 2009
  11. Seage GR et al. The relation between nitrite inhalants, unprotected receptive anal intercourse, and the risk of Human Immunodeficiency Virus infection. Am J Epidemiol 135(1):1-11, 1992
  12. Duesberg P et al. The chemical bases of the various AIDS epidemics: recreational drugs, anti-viral chemotherapy and malnutrition. J Biosci 28(4):383-412, 2003
  13. Schechter MT et al. HIV-1 and the aetiology of AIDS Lancet 341:658-659, 1993
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
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