YES and Osmolality


Osmolality refers to the number of dissolved particles per unit of water in a solution. Less particles of solute in proportion to water units means a less concentrated solution. Osmolality is important when it comes to personal lubricants and moisturisers because it gives information about the hydration status within our cells. The outer layer of our skin constantly works to balance osmolality between skin cells and the lubricant on the cell’s outside walls. Water moves freely back and forth across the cell membrane in response to the concentration of particles in the lubricant to balance the concentration on both sides.


  • So, if a lubricant has a higher osmolality/stronger concentration than human cells (hyper-osmotic), cells try to dilute the lubricant by releasing water. This can cause them to die as they become dehydrated and too concentrated. The result is skin irritation, skin damage and susceptibility to bacterial infection and STI contraction.
  • If a lubricant has a lower osmolality/weaker concentration than human cells (hypo-osmotic), cells try to pull water from the lubricant into the cell. Therefore, a slightly hypo-osmotic lubricant rehydrates tissues, but an extremely hypo-osmotic lubricant could cause cells to burst.
  • If a lubricant has the same concentration as bodily tissues it is applied to, it is called iso-osmotic.


YES products are formulated to the following osmolalities:

  • Vaginal lubricants: iso-osmotic to slightly hypo-osmotic with a similar concentration to delicate vaginal tissues
  • Vaginal moisturisers: iso-osmotic/identical with vaginal tissue concentration as it is present in the vagina for extended periods (1 to 3 days) and will release water as needed
  • Fertility lubricants: iso-osmotic/identical with semen to facilitate movement
  • Anal lubricants: iso-osmotic with anal tissues

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