#7 Contact lenses
It may be an item that is very obvious to those of us that wear contact lenses often, but for others, it is not really as easily recognizable that you shouldn’t be using water on contact lenses. Whether you’re helping a younger member of the family or explaining it to someone else, it’s great to keep in mind why you shouldn’t be cleaning it with just running water.
There’s a surprising amount of people who think you can just throw them in the liquid overnight and the contacts will be fine, but in reality, this is highly unsanitary. If it were that simple, ophthalmologists would not require you to purchase a contact lens solution after receiving your first pair of contacts. If left in water overnight, the lenses will end up with a lot of bacteria on them.
As you wear the lens, a part of it will be in contact with the air, and it will pick up foreign particles and bacteria. The contact lens solution will make sure to kill all those bacteria and discourage their spreading. Storing the contacts anywhere else will just favor and encourage the growth of bacteria in the colony. And when you put them back in, those will move to your cornea, and you can end up with a lot of ulcerations.
Not to mention that tap water is not sterile: you may end up adding other parasites or fungi to your lenses in addition to bacteria. And you truly do not want those pressed against your eyes the next day.