Wow, after starting to research into lubes with my last post, I realized how little I know. I also realized that other folks are looking for this information to be summarized as well. I have done more digging. AND this time I will provide references as I should have done in my prior post.
I enjoy learning the history of things, and in 2012 The World Health Organization (WHO) came out with a report on lubes. This report essentially details a lot of what I found in my literature review. That is, hyperosmolality negatively affects vaginal, cervical-vaginal, and colorectal tissue. This isn't necessarily perfectly clear in the literature, but it seems generally true. High concentrations of the substances I mentioned in the prior post: 1. glycerine/glycol, 2. propylene glycol, and 3. polyethylene glycol (PEG-8) disrupt vaginal and rectal tissue largely through their hyperosmolality, which disrupts the tissue integrity. Normal osmolality of the vagina is around 370 mOsm/kg. The WHO report suggests that lubes adhere to <1200 mOsm/kg. This recommendation holds true for rectal tissue. Disruption of tissue integrity seems to increase susceptibility to genital herpes, HIV, and bacterial vaginosis (which further increases risk of HIV, gonorrhea, trichomonas, pelvic inflammatory disease, and urinary tract infections).
Another factor, which I did not mention in the prior post is pH. Normal vaginal pH is acidic ranging from 3.2 - 4.5. The rectal pH is 5.5 - 7. The vagina has healthy bacteria that thrives and lives at this pH. Therefore, if you use a lube that has a dramatically different pH, you could be challenging that healthy bacteria in a bad way. There's also some other ingredients in lubes that tend to reduce the healthy vaginal bacteria. Without healthy bacteria, the vagina becomes more at risk for HIV, herpes simplex virus, chlamydia, gonorrhea, and bacterial vaginosis.
Other notable information that is relevant: many spermicidal lubes include something called nonoxynol-9 or N9. This is a known substance that breaks down vaginal integrity. It is used in many of the studies I cited as a negative control, or as a comparison of what is the worst. Other potentially harmful ingredients include: polyquarternary compounds and glycerol monolaurate (GML).
Lubes that have "warming" effects almost always are hyperosmolal. In reading through the studies on many common lubes: KY Jelly and Astroglide were often found to be pretty irritating especially vaginally. KY Jelly in particular has an ingredient that kills the healthy vaginal bacteria. Astroglide tends to be extra hyperosmolal.
Consistently neutral lubes include: Good Clean Love, Slippery Stuff, PRÉ.
The other thing to note is that silicone lubes are not absorbed. The testing on them is more limited, but it seems to be true that the sensitive tissues of the vagina and rectum are not disrupted by silicone lube due to its physical properties.
I covered lubes, vaginas, but what about SLUGS? Hang in there for this final nerdy note:
There has been some evolution in how the testing of lubes is being conducted. It used to be that there was a model using rabbit vaginas, however their vaginas have a pH of 7, therefore, that environment is quite dissimilar from a human vagina. So, now, there is use of a slug model. Yup. Slugs slough off their mucosal layers similarly to the vagina. And now you know.
1. World Health Organization. (2012). Use and procurement of additional lubricants for male and female condoms: WHO/UNFPA/FHI360: advisory note. World Health Organization. https://apps.who.int/iris/handle/10665/76580
2. Ayehunie, S., Wang, Y., Landry, T., Bogojevic, S., & Cone, R. A. (2018). Hyperosmolal vaginal LUBRICANTS markedly reduce Epithelial BARRIER properties in a Three-dimensional VAGINAL epithelium model. Toxicology Reports, 5, 134-140. doi:10.1016/j.toxrep.2017.12.011
3. Dezzutti, C. S., Brown, E. R., Moncla, B., Russo, J., Cost, M., Wang, L., . . . Rohan, L. C. (2012). Is wetter better? An evaluation of over-the-counter personal lubricants for safety and anti-hiv-1 activity. PLoS ONE, 7(11). doi:10.1371/journal.pone.0048328
4. Moench, T. R., Mumper, R. J., Hoen, T. E., Sun, M., & Cone, R. A. (2010). Microbicide excipients can greatly increase susceptibility to genital herpes transmission in the mouse. BMC Infectious Diseases, 10(1). doi:10.1186/1471-2334-10-331
5. Cunha, A., Machado, R., Palmeira-de-Oliveira, A., Martinez-de-Oliveira, J., Das Neves, J., & Palmeira-de-Oliveira, R. (2014). Characterization of commercially available vaginal lubricants: A safety perspective. Pharmaceutics, 6(3), 530-542. doi:10.3390/pharmaceutics6030530
6. Adriaens, E., & Remon, J. P. (2008). Mucosal irritation potential of personal lubricants relates to Product osmolality as detected by the Slug MUCOSAL IRRITATION ASSAY. Sexually Transmitted Diseases, 35(5), 512-516. doi:10.1097/olq.0b013e3181644669
7. DHONDT, M., ADRIAENS, E., ROEY, J., & REMON, J. (2005). The evaluation of the LOCAL tolerance of Vaginal formulations containing DAPIVIRINE using the Slug MUCOSAL irritation test and the rabbit Vaginal irritation test. European Journal of Pharmaceutics and Biopharmaceutics, 60(3), 419-425. doi:10.1016/j.ejpb.2005.01.012