What should I do with old perfume?

There are really a lot of old perfumes.

I'm wondering if it's okay to keep using old perfume. It's a perfume I bought a few years ago, and the scent feels a little different from before, and the color seems to have changed slightly as well.

I am worried about whether it is okay to spray this old perfume directly on my skin or if it might cause skin irritation. If it is difficult to use, I would like to know specific ways to utilize it—whether I should throw it away or if it can be used in other ways, such as as an air freshener in a closet or shoe cabinet.

Since they were all gifts, I feel like it would be a waste to throw them away easily, so I hesitate to do so.