The real difference between a lubricant and a moisturizer is duration. Lubricants coat the vagina to ease penetration, which adds comfort during intercourse. They provide a benefit at the time of use, but are not designed to last.
Moisturizers (like Yes, which we offer at MiddlesexMD) are designed to be longer lasting. They replenish and help maintain water content in the vagina, clinging to the vaginal walls so they are effective for several days. Mineral- and vegetable-oil-based moisturizers are not recommended because they can cause irritation, providing a habitat for abnormal bacteria. Vitamin E oil, on the other hand, can be a helpful ingredient.
Yes can be applied as a vaginal moisturizer every 3 days. Some women prefer more frequent use, others need it a little less often to stay comfortable. You can determine your own frequency with use.