Chances are slim, though, that your skinny jeans themselves will cause an overgrowth of yeast or bacteria. Theoretically, however, they could be one small part of the larger equation. They decrease breathability, helping trap heat and moisture in your vagina, which can promote an environment where yeast and bacteria thrive. It makes sense. But what you have on underneath those jeans is more important.
For women with chronic yeast or bacterial infections, something is clearly disturbing the pH of the vagina, it could be the detergent they’re using or underwear they're wearing. Underwear made of synthetic materials traps moisture, decreasing the airflow in that area. When you pair the two together, it could potentially make a greater impact than either factor itself. (Underwear made of wicking materials, like polyester, is good for a very sweaty workout, but not necessarily everyday use.)
So, what can you do to keep your vagina happy when you're squeezing into your favorite pants?
If you suffer from irritation, it may be worth switching to a skirt for a little bit or at least pants that don't cause friction, to see if it helps. All women, but especially those prone to irritation or yeast or bacterial infections, should wear plain cotton underwear and change it often.
Once a day should be enough, but if you're having excessive discharge, you should be changing it more frequently or using a panty liner and replacing it when it gets near full. If you're experiencing recurrent yeast or bacterial infections, or simply don't know your diagnosis, see your doctor to figure out the underlying cause. As easy as it is to point fingers when you're uncomfortable and desperate for an explanation, it's probably not your Levi's' fault.