Sex Lubricant Safety: Medical Studies List

This is a list of medical studies & health guidance that comment on sexual lubricant safety. Most relate to the osmolality of water-based personal lubricants (and also give pH levels for those lubes). The vast majority of studies which consider lubricant osmolality in depth demonstrate that high osmolality (high “concentration”) strips away the outer cell layers that are meant to shield the vagina, as well as the rectum, from harmful bacteria and viral infection.

This is a huge public health concern that’s often overlooked: So I’ve published a complete lube measurement table with certainly-safe options.

Not all studies are in 100% agreement about every detail in re how much damage a certain lubricant causes to tissue. I’ll point out potential issues with any data I find below. The vast majority of studies published over the past 20 years recognize and agree that high-osmolality lubricant damages the cells’ ability to protect themselves against outside pathogens [harmful germs]. As astrophysicist Neil DeGrasse Tyson says about scientific research and consensus, “If you went to your doctor and you have some ailment— The doctor says, ‘You can take this pill, which 3% of all research says will cure you; or you can take this pill, which 97% of all research says will cure you: Which one are you gonna walk away from the doctor’s office with? The 97% pill, of course.”1 Read for yourself below, or search the PubMed database and similar medical resources for “hyperosmolar lubricant,” etc., for a fuller picture.

Quick vocab lesson: The prefixes “hyper-,” “iso-,” and “hypo-” mean high, same-as, and low, respectively. The suffixes “-osmolal” (sometimes given as “osmolar”), “-tonic,” and “-osmotic” all carry the same meaning too: they’re about osmolality, a.k.a. concentration. So these terms are equal:

  • Iso-osmolal, iso-osmotic, isotonic, or even iso-osmolar: Has an osmolality that’s similar to healthy human tissues.
  • Hyperosmolal, hyperosmotic, hypertonic, hyperosmolar: Has an osmolality that’s higher than healthy human tissues.
  • Hypo-osmolal, hypo-osmotic, hypotonic, hypo-osmolar: Has an osmolality that’s lower than healthy human tissues.

I’ll cite and link to each study below, then give my quick recap in purple, then Quote: the study’s text directly. Vocab note: STI = sexually transmitted infection, i.e., typically bacteria and viruses primarily passed via sex.

Studies Showing Hyperosmolal Lubricants Damage Human Samples:

  • Ayehunie, Seyoum, et al., “Hyperosmolal vaginal lubricants markedly reduce epithelial barrier properties…,” in Toxicology Reports 5 (2018): 134–140. This study is the one I recommend you check out—at least the Intro, the Discussion, and the Conclusion—if you only have a short amount of time. It explains how damage to the epithelial barrier (protective cell layers) has been tied to infections like bacterial vaginosis. Then, the study surveys “mucosal irritation” via testing lubricants neat (not diluted) on human vaginal and colorectal (🍑) tissues, as well as testing epithelial barrier integrity via electrical resistance; and it includes cellular enlargements of vaginal-ectocervical tissue covered with Good Clean Love and Aloe Cadabra, plus other more-toxic lubes like Astroglide, KY, and ID Glide. Quotes: “A well-characterized three-dimensional human vaginal epithelium tissue model demonstrated that vaginal lubricants with osmolality greater than 4 times that of vasginal [sic] fluid (>1500 mOsm/Kg) markedly reduce epithelial barrier properties and showed damage in tissue structure.… No epithelial damage to these layers was observed for hypo- and iso-osmolal lubricants with osmolality of <400 mOsm/Kg.” On how it’s possible that many individuals can use hyperosmotic lubricants and not feel any damage: “Historically, the significance of a highly toxic agent, the detergent nonoxynol-9, was not adequately realized until after performing large HIV prevention trials of N9 [23]. This detergent was, and still is, used as a vaginal contraceptive. Despite its significant toxic effects, it does not cause obvious pain or discomfort in most users. Similarly, hyperosmolal lubricants cause little or no obvious pain or discomfort to most users. But they cause marked toxicity to the human colorectal epithelium [3]. They increase susceptibility to genital herpes (HSV) infections in the mouse/vaginal HSV model [5] and they cause obvious toxic effects in the slug mucosal model….” On ingredients to avoid: “In this study, lubricants containing glycerin/glycol, propylene glycol, and Polyethylene glycol (PEG-8) as one of the top four ingredients were associated with marked reduction in barrier properties and tissue morphological damage.” [I would also note that many lube makers are now replacing propylene glycol with propanediol in recent years, because the bad news about propylene glycol in lubes has gotten out: yet, propanediol and propylene glycol are so structurally similar, propylene glycol’s chemical name is propanediol-1,2.]
  • Wilkinson, Ellen M., et al., “Personal and Clinical Vaginal Lubricants: Impact on Local Vaginal Microenvironment…”, in Journal of Infectious Diseases 220, no. 12 (2019): pp. 2009–2018. Employed both single-layer and a 3-D cell cultures, of vaginal tissue onto which 7 lubes were applied; Good Clean Love Almost Naked and 6 other lubes including KY, most of which had glycerin as the second ingredient. See Table 1. Lubes were applied at a 1:10 dilution for 24 hours. Conclusion: “These findings indicate that hyperosmolar lubricants alter VEC [vaginal epithelial cell] morphology and are selectively cytotoxic [=toxic to living cells], inflammatory, and barrier disrupting in the 3-D VEC model.” Interestingly, this study also discusses in depth why the US FDA’s lube approval model, on the rabbit vagina, is flawed—which would explain why even doctor’s offices apply hyperosmolal lubes to gyno patients: “No current animal model system accurately reflects the human vaginal microenvironment.”
  • Edwards, D., and N. Panay, “Treating vulvovaginal atrophy/genitourinary syndrome of menopause: how important is vaginal lubricant and moisturizer composition?” in Climateric 19, no. 2 (2016): 151–161. This literature review has great charts, and really, applies to how lubes affect vaginal tissues at any age. Figure 1 lists pH & osmolality values for a fair amount of lubricants; but note that formulations may have changed in some cases since 2015 when this was written: like how Good Clean Love Almost Naked is now slightly more acidic for vaginal balance. Interesting note: In Table 1, this study includes a note that evaluates very hypo-osmolal lubes (not much thicker than water!) as equally harmful to hyperosmolal lubes; this is based on Adriaens, below: “Values represent hypo-osmolar (< 32 mOsm/kg) or hyperosmolar preparations that exceed the ideal osmolality threshold….” Conclusion: “Non-physiological [=not normally healthy] pH and osmolality, and the presence of excipients such as parabens and microbicides, are associated with a variety of proven or potential detrimental effects… It is advised that women choose a product that is optimally balanced in terms of both osmolality and pH and is physiologically most similar to natural vaginal secretions.”
  • Adriaens, Els, & Jean Paul Remon, “Mucosal Irritation Potential of Personal Lubricants Relates to Product Osmolality,” Sexually Transmitted Diseases 35, no. 5 (May 2008): 512–516. This study uses a slug mucosal assay, which tracks irritation not on humans, but which can predict burning and itching in human cavities where mucus is produced (like the vaginal mucosa [tissues] & in the butt). The study authors propose that the slug model can better indicate irritation in actual humans than the rabbit model (employed by the U.S. FDA for lubricant approval) does. Five lubricants, including KY and Astroglide, were tested for mucosal irritation vs. osmolality level. Quote: “The irritation potency (assessed by the mucus production) of the lubricants showed a significant, quadratic relationship with the product osmolality…. Femglide, a hypo-osmotic lubricant (32 mOsm/kg), caused a negative mucus production. Pré, an iso-osmotic lubricant (316 mOsm/kg), caused no changes. Two moderately hyperosmotic lubricants, Replens and K-Y jelly (2143 and 2463 mOsm/kg), induced mild and moderate irritation, respectively. The highly hyperosmotic lubricant Astroglide (5848 mOsm/kg) resulted in severe irritation and tissue damage.”
  • Fuchs, Edward J., et al., “Hyperosmolar sexual lubricant causes epithelial damage in the distal colon…” in Journal of Infectious Diseases 195, no. 5 (March 2007): 703–10. This study tested hyperosmolal lubes inside actual human patients’ asses. It then measured “Epithelial denudation 10 cm from the anus” (that is, just under 4 inches inside the butt, before the sigmoid bend that transitions between rectum and colon). Quotes: “These findings suggest that the administration of a hyperosmolar gel is associated with epithelial ‘injury’ most pronounced at the site of the initial, most-concentrated exposure to an osmotic gradient…. Given that epithelial injury is seen within 1–1.5 h after lubricant application, damage is present not long after, if not during, anal intercourse and potential exposure to infectious seminal fluid…. Our findings raise cautionary flags about the development of hyperosmolar microbicide gel vehicles. More immediately, given that the majority of lubricants we measured are hyperosmolar, the potential for hyperosmolarity-induced epithelial damage and possibly increased HIV susceptibility raises significant concern. If this finding can be generalized to hyperosmolar enema preparations, in which the issues of volume and mucosal access are more likely sufficient to induce mucosal damage, the concern is even greater.”

World Health Organization Guidelines for Lube

In 2012, the World Health Organization published an advisory note based on an April 2011 meeting in re sexual lubricant safety, and how it affected condom use and STI prevention. The WHO was concerned about how high-osmolality lubricants can cause both vaginal and anal damage, and thus lead to more infections among lube users; but on the contrary, water-based lube is a positive, they note on p. 1, because it reduces condom breakage.

Important points from this transnational health organization, which in recent years has been known to issue faster, more initially accurate info than the US FDA when it comes to new infections:

  • “Recent studies have identified a number of potential safety issues with personal lubricants. Much of this new information is based on laboratory (in vitro) testing. Several papers (13–16) suggest that lubricants with high osmolality might cause vaginal and anal epithelial damage. Confirmation that lubricants with high osmolality can cause epithelium damage when applied rectally to humans has been demonstrated in a group of 10 volunteers (15). Epithelial damage could in turn increase the risk of infection, for example by HIV and other sexually transmitted infections (STIs)….. Most commercial personal lubricants have high osmolalities (2000–6000 mOsm/kg).”
  • “Ideally, the osmolality of a personal lubricant should not exceed 380 mOsm/Kg to minimize any risk of epithelial damage. Given that most commercial lubricants significantly exceed this value, imposing such a limit at this time could severely limit the options for sourcing personal lubricants for sector procurement. It is therefore recommended on an interim basis that procurement agencies should source lubricants with osmolalities of not greater than 1200 mOm/kg…. Adopting an upper limit of 1200 mOsm/kg will have a significant impact on the number of available commercial lubricants that can be currently procured. Most current commercial lubricants, as reported above, have osmolalities in the 2000–6000 mOsm/kg range. The formulation of low osmolal lubricants does not, however, present any significant technical challenges.”
  • “The primary factor determining the osmolality of the majority of lubricants is the concentration of glycol. Glycols are added as humecants/moisturizers. Glycerol and propylene glycol are most commonly used.”
  • “The pH of the healthy vagina is normally in the range 3.8–4.5. The pH of the rectum is closer to neutral (pH 7). High vaginal pH can lead to an increase in the risk of bacterial vaginosis. High pH is also more supportive of HIV survival. Ideally therefore a vaginal lubricant should have a pH of about 4.5 and a rectal lubricant of about 5.5 to 7. It is unfortunate that these optimum requirements cannot be bridged in a single lubricant. The preservation of water-based lubricants is easier if the pH is maintained below 7.”

ANAL: Studies on Hyperosmolal Lubricants and/or STI Susceptibility

Hyperosmolal lubricants don’t just affect the vagina. Anal lube research is often centered around the (legitimately) most-feared anal STI: HIV-AIDS; but expands to other STIs, too. But even if someone is only engaging in sex with a sex toy, would they really want to experience the loss of protective skin layers inside the rectum? See also Fuchs et al., “Hyperosmolar sexual lubricant causes epithelial damage….”

  • Haaland, Richard E., et al., “Repeated rectal application of a hyperosmolar lubricant is associated with microbiota shifts but does not affect PrEP drug concentrations…” in Journal of the International AIDS Society 21, no. 10 (October 2018): e25199. This is an observational study on men who have sex with men, which found that hyperosmolal lubes don’t affect oral PrEP concentrations (an oral pill that protects against HIV acquisition); but hyperosmolal lubes are linked to more potentially inflammatory bacteria (Prevotella) in the rectum. Conclusion: “Repeated application of a hyperosmolar lubricant did not affect mucosal PrEP drug concentrations among MSM, but was associated with changes in the rectal microbiome. While hyperosmolar personal lubricants may exacerbate damage to the rectal mucosa during RAI and lead to shifts in the rectal mucosal microbiota to favour Prevotella over Bacteroides.”
  • Kevin Rebe et al., “Sexual lubricants in South Africa may potentially disrupt mucosal surfaces…,” in South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde 104, no. 1 (December 2013): 49–51. Quick study that simply gives osmolality of 8 popular lubricants in South Africa, under the assumption that hyperosmolal equals “damaging.” Quote: “Seven (88%) of the commercial lubricants had high osmolalities, with two products approaching 10 000 mosmol/l, far in excess of serum which has an osmolality of ~280 mosmol/l.” Conclusion: “The results of this study show that many of the top-selling brands of water-based sexual lubricants available in SA are hyperosmolar. Given that hyperosmolar products have been shown in vitro and in vivo to cause epithelial injury, they may have the potential to increase HIV acquisition and transmission, if they are used during UAI [unprotected anal intercourse]. Awareness needs to be raised about the mucosal safety of lubricants designed for use during anal sex.”
  • Begay, Othello, et al., “Personal Lubricants That Can Cause Rectal Epithelial Cell Damage and Enhance HIV Type 1 Replication in Vitro,” AIDS Research and Human Retroviruses 27, no. 9 (2011): 1019–1024. This one tested 41 lubes against a toxic and non-toxic control, on human colon cells and cervical cells (drawn from carcinomas). Lubricants were diluted to some degree; and cells were also tested via electrical resistance, to show how well their epithelial barriers were holding up. The study found that four different Astroglide lubes with polyquaternium-15 enhanced HIV replication. Now, over a decade later, Astroglide Liquid lubes are still using this agent of increased viral replication!!! Quotes: “Previous studies documented anti-HIV-1 activity of Astroglide brand lubricants,10 but based on our findings, this appears to be due to the toxic effect of the product and not true antiviral effect. As seen in N-9 studies,5,6 although a compound has the potential to inactivate free HIV-1 particles and disrupt the cellular membrane of cells infected with HIV-1, the potential toxic effects outweigh the potential benefits. Herein we document that most of the 41 lubricants tested exhibited TI values that reflected the impact of cellular toxicity and not specific antiviral activity. Recent studies have also shown a correlation between lubricant osmolality and rectal toxicity.6 Supporting this conclusion, our results show that a majority of the lubricants reduced the electrical resistance passing through the cellular monolayer indicating a loss of integrity.”
  • Sudol, Kristin M., and David M. Phillips, “Relative Safety of Sexual Lubricants for Rectal Intercourse,” in Sexually Transmitted Diseases 31, no. 6 (June 2004): 346–349. This study used mice whose rectums were dosed with dilute amounts of 6 different lubricants. It concluded that KY-Plus leads to an increase in HIV and herpes infection rates. It does not give any osmolality ratings. Quote: “We caution that any anti-HIV properties are most likely related to general cytotoxicity. The formulations with the greatest anti-HIV activity are likely to breach the delicate epithelia of the rectum and lower intestinal tract. Thus, although they could have some anti-HIV activity, these products should not be used as rectal lubricants.”
  • Vishwanathan, Sundaram A., et al., “Rectal Application of a Highly Osmolar Personal Lubricant in a Macaque Model Induces Acute Cytotoxicity but Does Not Increase Risk of SHIV Infection,” in PLoS One 10, no. 4 (2015): e0120021. aaThis one has a great general overview; the tests were to apply a very hyperosmolal lube to macaque monkeys, via “non-traumatic applications of lubricant.” lIn general, lube application increased inflammatory markers in the short term, but the monkeys’ butts were able to recover post-application. Intro overview: “An emerging hypothesis is that the hyper-osmolality of many water-based lubricants correlates with epithelial tissue damage they induce [913]. When epithelial cells are subjected to a hyper-osmolar environment, they release water, leading to cell shrinkage and damage. This can cause breaks in epithelial integrity, and could thereby facilitate entry of invading pathogens, including HIV, to underlying tissues where susceptible HIV target cells reside. Hyper-osmolality is caused by high concentrations of salts in lubricants, even if the chemicals are considered safe in lower concentrations. Results from several studies support an association of lubricant osmolality with cytotoxicity: Aqueous hyper-osmolar lubricants have cytotoxic effects on epithelial cells in in vitro models [10,14], in ex vivo tissue explants models [9], and in slug mucosal irritation assays [13]. Importantly, the one observational study in humans of a hyper-osmolar mixture of lubricants demonstrated epithelial damage in the human colon [12]. In vivo studies of rectal hyper-osmolar lubricant use in mice also documented rectal tissue sloughing, a sign of epithelial tissue damage [11]. In addition to hyper-osmolality, lubricants may have other properties that may affect the genital environment and susceptibility to infection [15].” Conclusions: “To determine the effects of lubricant use on inflammation, we analyzed cytokines and other inflammatory markers from rectal secretions. Numerous cytokines peaked significantly at acute time points post-lubrication [TNF-α (p = 0.024), IL-12 (p = 0.016), IL-15 (p = 0.015), G-CSF (p = 0.013), sCD40 (p = 0.050), IL-4 (p = 0.009), MCP-1 (p = 0.026), MIP-1α (p = 0.014), and IL-1β (p = 0.008); Table 1]. Fig. 1, B and C show TNF-α induction as an example for a pro-inflammatory cytokine upregulated at acute time points after lubricant use, but not longitudinally during the six weeks of treatment. Rectal TNF-α peaked 30 minutes after the second weekly lubricant application. Cytokines were not upregulated compared to baseline in longitudinal samples collected over six weeks, suggesting no persistent or cumulative effect of frequent lubricant use on these inflammatory markers.” “The median rectal pH was 7.9 (S3 Fig.), both before and after lubricant treatment (p = 0.4230; unpaired 2-tailed Mann-Whitney test), despite the study lubricant’s pH of 4.4.” “inflammation and cytokine induction were largely short-lived (peaking at 30 minutes, and subsiding within two hours after lubricant use), and less pronounced than we have previously observed during rectal co-infection with Chlamydia trachomatis in a similar macaque model [24]. Other cytotoxicity parameters such as bleeding and tissue sloughing were documented after lubricant use, but were not significantly upregulated.”

VAGINAL: More on Osmolality and the Vaginal Microbiome

The vaginal “ecosystem,” or microbiome, is the only human microbiome that is not healthier when it’s diverse. The vagina should be dominated by a strain of Lactobacillus bacteria (preferably “L. crispatus,” the “Lactobacillus spp.” most frequently associated with vaginal wellness). Why? Well, these helpful Lactobacteria acidify the vagina, lowering pH to protect the always-moist vaginal tissues (1) from pathogenic bacteria that can’t survive in such an acidic environment: like the Gardnerella vaginalis that most-often causes bacterial vaginosis, producing foul smells, odd discharge, and/or burning; and (2) from viral infections acquired from any sex partner(s). Any added protection there is important because, as I believe we all should’ve learned since COVID, viral DNA is insidious: Herpes remains in the body for life and may cause recurring blisters and outbreaks, while HPV causes 99% of cervical cancer (plus some uterine and vaginal cancers), and HIV remains a for-real immune issue even though antiretroviral treatmens have made it less deadly than it was (in the 1980s).

  • Happel, Anna-Ursula, et al., “Considerations for Choosing Soluble Immune Markers to Determine Safety of Novel Vaginal Products,” in Gynecology, a section of Frontiers in Reproductive Health (May 2022). This is literature review with guidelines for new vaginal products. It gives detailed data about the vaginal microbiome, collected from other studies, including measurements for different immune cell markers in vaginal samples, across continents. It includes the “Cautionary Tale of Nonoxynol-9,” an antimicrobial presumed to be safe for decades until scientists finally released it “showed a 2-fold greater increased in HIV acquisition [and] an increase in genital mucosal inflammation. New product guidelines are: “The most well-described consideration for vaginal products is avoidance of hypertonic [=hyperosmolal] formulations which are cytotoxic [=toxic to cells], increase epithelial cell shedding and decrease epithelial integrity [=negatively alter protective cell barriers]. Inflammation in the human female genital tract, regardless of the cause or presence of symptoms [i.e., even if the person doesn’t feel it!], creates an environment associated with a range of adverse health outcomes, including increased risk of HIV acquisition. Any new product should ensure no off-target, pro-inflammatory effects.”
  • N. Potter and N. Panay, “Vaginal lubricants and moisturizers: a review into use, efficacy, and safety,Climateratic 21, no. 1 (2021): 19–24. This study states as a given that menopausal women should be directed toward iso-osmotic and pH-balanced lubricants for vaginal use: “Over-the-counter vaginal moisturizers and lubricants can ease the symptoms of VVA [vulvovaginal atrophy, typically a menopausal condition]. However, their chemical composition varies enormously and some are known to cause detrimental effects due to unphysiological pH, osmolality, and additives…. Women should be directed toward products that are as ‘body-similar’ as possible to vaginal secretions in terms of pH and osmolality.”
  • Nicole, Wendee, “…Chemicals in Feminine Hygiene Products and Personal Lubricants,” in Environmental Health Perspectives 122, no. 3 (2014): A70–A75, section “Lubricants and STI Transmission.” An overview citing other sources. Quotes: “A lot of the aqueous-based lubricants are hyperosmolar, [which means] they tend to pull water out of your cells, and that causes the cells to shrink and shrivel,” she explains. “When we looked at human tissue, the cervical epithelium fractured off, and the rectal mucosa came off as well.” “Cone has reported evidence that glycerin, glycerol monolaurate, polyethylene glycol, and propylene glycol—all used as excipients, or bulking agents, in lubricants—increased the transmission of genital herpes infections in the mouse vagina.2 Cone and colleagues wrote, ‘Although excipients are often called “inactive ingredients” and are widely considered to be benign, these ingredients do have activities and toxicities.’2” 
  • Tuddenham, Susan, et al., “Vaginal cytokine profile and microbiota before and after lubricant use…” in BMC Infectious Diseases 21 (2021): 973. This observational study recruited 44 participants, divided into a lube group and a control group (who didn’t use condoms), from which vaginal swabs were taken before and after sex for 10 weeks. The types of lubricant that the participants used wasn’t specified by the study, so we can assume that there’s a ≈99.8% chance they were hyperosmolal. Quotes: “There was a trend toward decreases in relative abundance of L. crispatus [the most-protective vaginal microbe] following use of lubricant. Future larger studies that take into account osmolarity and composition of lubricants may provide additional insights.”
  • O’Hanlon, D. Elizabeth, et al., “Observational cohort study of the effect of a single lubricant exposure during transvaginal ultrasound on cell-shedding from the vaginal epithelium,” in PLoS One 16, no. 5 (2021): e0250153. This study realizes that hyperosmolal lubricants are used in doctor’s offices, like on ultrasound wands at your OBGYN. It states, “This preliminary data indicates hypertonic vaginal lubricants may increase vaginal epithelial cell shedding.” It includes nice graphic of the vaginal epithelium, with its 4 distinct layers. The lubricant applied to patients via ultrasound wand had a 2,400 mOsm/kg osmolality. The authors took 3 vaginal samples after lube introduction occurred: 6–12 hours after, 1 week after, and 2 weeks after; as well as a sample pre-ultrasound. They surmised that the shedding of epithelial cell layers happened prior to the first 6-to-12-hour-later collection point: “Rapid detachment/shedding and subsequent clearance of VE [vaginal epithelial] cells may have occurred very soon after lubricant exposure, resulting in the observed decreases in cell maturity. This rapid loss hypothesis is supported by published in vivo research showing that rectal epithelial denudation caused by hyperosmolal lubricants increases within 1.5 hours of lubricant application [32]. Future studies could include additional sampling time-points immediately following exposure to lubricant to investigate the rapidity of the shedding response. The osmolality of the lubricant used in this study (approximately 2,400 mOsm/kg [27]) is in the middle of the range for personal lubricants [32] and the length of exposure (all TVUS procedures were completed in approximately 30 minutes) is reasonably consistent with use of lubricants for sexual activities. The effects observed in this study are, therefore, likely to pertain to non-clinical use of many other personal lubricants as well. Additionally, while it is not possible with this observational study design to separate the effects of lubricant from other possible factors, including effects of the TVUS probe or SoftDiscTM collection device, in vitro studies support that hyperosmolal lubricants alone are capable of reducing epithelial cell barrier integrity and causing tissue morphological damage [2938].”
  • Laniewski, Pawel, et al., “Clinical and personal lubricants impact growth of vaginal Lactobacillus species and colonization of vaginal epithelial cells,” in Sexually Transmitted Diseases 48, no. 1 (January 2021): 63–70. This study cultured vag cells with various strains of protective Lactobacillus, and then applied dilute amounts of lubricant; and, alternately, applied lubricant and then applied Lactobacillus, which results I would not trust because it’s unrealistic, the vagina isn’t going to suddenly pick up non-preexisting Lactobacillus soon after lube use (the Lactobacillus should be in place already in healthy vagina). It does very clearly point out that antimicrobial additives like parabens and chlorhexidine gluconate (CHG) damage bacterial growth. The study classifies KY Jelly’s 2500 osmolality as “[lacking] association to high osmolality,” which is strange. In any case, the one iso-osmotic lube they tested, Good Clean Love Almost Naked. Quote: “In contrast, GCL Almost Naked did not impact the colonization at any tested time points compared to untreated or glycerol controls.”
  • Brown, Joelle M., et al., “Intravaginal Practices and Risk of Bacterial Vaginosis and Candidiasis Infection…,” in Obstetrics & Gynecology 121, no. 4 (April 2013): 773–780. This is an observational study of real people that correlates oil in the vagina with yeast infection (vulvovaginal candidiasis). Unspecified “oils” were placed in a different category than “petroleum jelly” (like Vaseline); and we have no idea what specific type of “oils” participants used. Quote: “We enrolled 141 women. Two thirds (66%) reported an intravaginal practice over the past month…. The most commonly reported practices included insertion of commercial sexual lubricants (70%), petroleum jelly (17%), and oils (13%). In univariable analysis, intravaginal use of oils was associated with Candida species colonization (44.4% compared with 5%, P<.01). In multivariable analysis, women reporting intravaginal use of petroleum jelly over the past month were 2.2 times more likely to test positive for bacterial vaginosis.”
  • Tuddenham et al., “Vaginal cytokine profile and microbiota before and after lubricant use…,” BMC Infectious Diseases 21, no. 1 (2021): 973. The microbiomes of 22 women who used any type of lubricant at home (thus, a very high probability the lubricants were hyperosmolal ones) were studied vs. the microbiomes of the same number of control subjects (no lube use). Statistically there were no major differences in the vaginal samples of the two groups, yet “Post sexual activity, the mean relative abundance of L. crispatus decreased for those who used lubricants (particularly those who were L. iners-dominated prior to exposure).” This is not good, because L. crispatus is more protective against pathogens (bacterial vaginosis and/or sexually transmitted infections) than L. iners is.
  • Hung, Kristin J., et al., “Effect of commercial vaginal products on the growth of uropathogenic and commensal vaginal bacteria,” in Scientific Reports 10, no. 1 (May 2020): 7625. This study is interesting but not conclusive, since it includes a lot of caveats about whether the results are applicable in vivo (in live humans) due to the 1:100 dilution ratio (1 part lube + 100 parts saline) used on vaginal tissue cultures. They tested 5 lubes, including KY Jelly new formula; coconut oil; a Replens water-based with glycerin, mineral oil, and palm oil in it; and a Replens 2-ingredient silicone lube, to see how it affected E. coli (which is unhealthy in the genitals) and L. crispatus (which is the one germ you absolutely want inside your vagina). Basically, two of the lubes were so toxic that they killed good bacteria even when only applied in a less-than-1% solution. Conclusion: “All products except for coconut oil significantly inhibited growth of laboratory and clinical strains of Escherichia coli (p < 0.02). Only two products (Replens Long-Lasting moisturizer [the water-based with glycerin, mineral oil, and a paraben] and Trimo-San [meant to prevent “odor,” but it’s so bad it’s not even FDA approved]) significantly inhibited growth of Lactobacillus crispatus (p < 0.01) [❌], while the product Replens Silky Smooth [the silicone lube] stimulated growth (p < 0.01) [✅].” But note: “Our study is limited by the lack of a better human vaginal model. The 1:100 product dilution needed to allow vaginal epithelial viability is not realistically translated to clinical use…. We did not assess mechanisms for the inhibitory effects, which could range from chemical toxicity to pH to osmolality…. At the 1:100 dilution no products inhibited the growth of Lactobacillus spp., thus we were unable to assess how the presence of human vaginal epithelial cells modified lubricant inhibition of Lactobacillus spp.”
  • Dezzutti, Charlene S., et al., “Is Wetter Better? An Evaluation of Over-the-Counter Personal Lubricants for Safety and Anti-HIV-1 Activity,” in PLoS ONE 7, no. 11 (2012): e48328. This is a fairly readable study that took vaginal and colorectal tissue samples and cultured them, then applied 13 different different lubricants to see the effects. As with other ex-vivo tissue sample models, the lubricants needed to be diluted (from 1∶10, to 1∶10,000) to keep the tissues viable, thus creating a little uncertainty about whether living humans wouldn’t get a lot more effects from lubricant application. This study measures an old version of Sliquid Organic Naturals, with a different first ingredient, a different preservative, and a much higher pH (6.8 in the old version, vs. 4.4 in the current [2022] Sliquid Organics Natural). Despite giving great measurements in Table 1, the study doesn’t discuss the impact of pH on cells, nor does it recognize that parabens can cause loss of protective bacteria: For example, the study says, “it is not clear why the L. jensenii were sensitive to Replens” [which contained methylparaben, plus glycerin as the first ingredient, followed by mineral oil and hydrogenated palm oil]. There are a lot of different tests going on in this same article, with little discussion of individual lubricant ingredients, unfortunately. Quotes & conclusions: “Hyperosmolar products lead to epithelial disruption [32][33]. This is important because the mucosal epithelium is a functional barrier against potential pathogens [34][35]…. Histological evaluation showed stripping/fracture of the colorectal and ectocervical epithelium by most of the hyperosmolar products…. Good Clean Love and PRÉ – iso-osmolar gels – retained tissue viability and epithelium. The silicone-based products showed no effect on tissue viability or the epithelium. Collectively, the nearly iso-osmolar and silicone-based lubricants were the safest for epithelial cells and mucosal tissues.”
  • Ana Raquel Cunha et al., “Characterization of Commercially Available Vaginal Lubricants: A Safety Perspective,” Pharmaceutics 6, no. 3 (2014): 530–42. Attempted to test whether 12 commercial lubricants were toxic to human cervical tissue, but the lubes were diluted to 20% (max!) when they were cultured. Quotes: “Gel concentrations higher than 20% were not tested, as the viscosity of obtained dilutions was found impracticable for cytotoxicity testing.” “None of the OTC lubricants tested in our work presented near iso-osmolality, which further limits the analysis.” “These last, somewhat divergent results [from Dezzutti, “Is Wetter Better?”] seem to highlight the limitations of cell toxicity assessment methods [like the one used in this study], particularly related to their correlation with ex vivo or even in vivo situations, thus recommending caution when extrapolating data.” “No definite correlation between gel pH or osmolality and cytotoxicity were found. Individual composition for tested products, as well as regional formulation variability, seems to be essential to undertake any specific cause-effect analysis. Further characterization is also deemed necessary in order to fully understand the potential hazard of the tested products, namely condom compatibility and safety to microbiota.”

On Douching

Douching is not a good thing: especially for the vagina, it’s awful. This fact is so well-established, I don’t even feel the need to pull up authoritative resources saying that vaginal douching leads to bacterial infection, increased STI susceptibility, and more. Don’t wash those good microbes out!

Anal douching is quite popular, as people feel the need to be “clean” for play, like to not get fecal traces on their toys, or on a partner’s penis. Here are a couple studies that cover the negative effect of anal douching and STI transmission.

  • Li, Peiyang, et al., “Association between rectal douching and HIV and other sexually transmitted infections among men who have sex with men: a systematic review and meta-analysis,” in Sexually Transmitted Infections 95, no. 6 (September 2019): 428–36. Quote:Results: Twenty-eight eligible studies were identified in our review, of which 24 (20 398 participants) were included in the meta-analysis. Rectal douching was associated with increased odds of infection with HIV (OR 2.80, 95% CI 2.32 to 3.39), and any STI other than HIV (including hepatitis B virus (HBV), hepatitis C virus (HCV), chlamydia, gonorrhoea, syphilis and human papillomavirus) (OR 2.46, 95% CI 1.95 to 3.11) among MSM. For specific STIs, douching was associated with increased odds of viral hepatitis (HBV, HCV) (OR 3.29, 95% CI 2.79 to 3.87), and chlamydia or gonorrhoea (OR 3.25, 95% CI 2.02 to 5.23). These associations remained significant in studies that adjusted for potential confounders. Conclusion: Rectal douching may put MSM at increased risk for infection with HIV and other STIs. Longitudinal studies are needed to clarify this association, and health education materials should inform men of the potential for increased risk of infection with rectal douching.”
  • Fuchs et al., “Hyperosmolar sexual lubricant causes epithelial damage in the distal colon…” says, “Early epidemiologic studies suggested that rectal douching is a strong predictor of HIV and hepatitis B virus infection, and MSM focus groups indicated that hyperosmolar enemas are commonly used for such douching.”

Even if someone is douching only to play with a body-safe sex toy, they are still washing out good bacteria: the rectum is the very end of the gut microbiome. The same as with hyperosmolal lubricants, it’s preferable to not mess with that natural balance.

Other Online Sources in Re Lube Osmolality

Oh, the Internet… A wealth of information, which is beautiful; but it’s also important to know that not all info is 100% accurate, so look at each source’s specific statements and whether each is supported by a wide range of other reliable sources.

Sutil: The Lube Maker Who Says Osmolality Doesn’t Matter

Sutil is one of these companies using “natural” ingredients from “botanical sources,” which they claim are better for your body. That’s fine; I’m sure most people would agree that organic produce is healthier because it shouldn’t have any pesticides on it. But as far as lubricant goes, more natural ingredients don’t necessarily make for a better product: you can’t just throw a bunch of plants later in the ingredient list, and claim that outweighs how the lube may be “shriveling” protective cellular barriers.

It’s a widely accepted truth that high osmolality (as well as specifically toxic ingredients) will cause the surface layers of vaginal and anal tissues to slough off and/or will decrease the electrical resistance of those epithelial layers: opening them up to damage by pathogenic [=bad] microbes, during and immediately after lubricant use.

But in 2018, Sutil made the bold statement to sex toy blogger SuperSmashCache:

We have stopped talking about osmolality because after spending over two years researching, reformulating and working with different labs we and other research scientists have come to the conclusion that the research on osmolality is inconclusive.

—Sutil’s reported email, in “Flavored Hathor/SUTIL Body Glide lube review,” published October 2018 & last updated January 2022

Now, I understand some confusion and lack of clarity as far as the different testing models go; lubricants need to be diluted in extracted (ex-vivo) vaginal & colorectal tissue tests to keep those cells alive to be measured; while animal testing models can’t re-create human holes, either. However, the preponderance of the data does indicate a negative, and even cytotoxic, impact from very-hyperosmolal lubricant application. It’s amazing to me that the World Health Organization could put out a very clear statement on this front, literally trying to save people’s health and even lives [given the toll of HIV-AIDS in different parts of the world], and there are still lubricant makers out there trying to claim the W.H.O.’s take doesn’t mean anything.

And keep in mind that Sutil displayed absolutely no data from these “other research scientists” they claim to have consulted with, to make their point. Show me studies or some kind of valid data. Because I know when I go onto PubMed and search “sexual lubricant osmolality,” I get studies like the ones listed above. No published scientist is out there saying, “We just stopped talking about lubricant osmolality, we didn’t think it was a thing that mattered.”

No one has found Good Clean Love (or Aloe Cadabra) to be damaging after hours’ worth of exposure.

So what is the osmolality of Sutil Lubricant? I’ll take a moment here to note that the osmolality of all Good Clean Love products is between 260 and 370 mOsm/kg osmolality, while Sutil Luxe glide, with propanediol as its second ingredient, is between 2,300 and 2,400. That makes Sutil over 6 times as osmotically concentrated as Good Clean Love’s highest-osmolality lube (a hybrid which also contains propanediol, but at less than 1%).

If Sutil had nothing to hide, they would list their Sutil lubricants’ osmolality, and give us information on why those levels are not harmful.

Good Clean Love’s Info

Good Clean Love’s blog has an article explaining hypo-, iso-, and hyper-osmality with a little bar graph showing how osmolality rises in different lubricants. The article is short, clear, and simple to understand.

Obviously, Good Clean Love has a vested interest in consumers caring about osmolality. But I applaud how their lubricants are consistently backed by scientific studies, and how they do release accurate data about the pH and the osmolality of all their products. I know, I’ve tested them with my own osmometer and pH meter—but normal folks shouldn’t have to do that, and GCL puts the information out there so you can make an educated choice without investing in expensive scientific equipment.

“Bad Vibes” Science of Lubricants

Bad Vibes’ Science of Lubricants page gives nice, clear graphics and osmolality explanation.

But do note that the Bad Vibes post is about 10 years old (I’m writing in 2022), and the pH levels of the last lubricants in the section “Average pH levels:” are no longer accurate. See my pH test results performed in July 2022.

Dangerous Lilly’s Classic Lube Guide

I believe Dangerous Lilly’s lubricant page, published nearly a decade ago, was how most of us sex toy enthusiasts were first introduced to the issue of personal lube safety. It’s a detailed post that draws images and data from the retailer Smitten Kitten’s resources (Smitten Kitten also published the site above, in 2005).

Stay Safe, My Friends!!!

  1. Quote from “Will America’s disregard for science be the end of its reign?” by Big Think YouTube channel, October 3, 2020; start just after 8 minutes here for context along with DeGrasse Tyson’s quote, which is about the human origins of climate change, but which can be extended to any scientific truth established through repeated and ongoing collected data and comparative research.

2 thoughts on “Sex Lubricant Safety: Medical Studies List”

    • You are correct, I am finishing the images on that piece just right now, check back in 2 hours! Got a little overeager to publish the studies list 😀. The full 3-part series will be up later tonight.

      Edit: It’s all up now! Thank u for reading.


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