You should keep a Band-Aid in your wallet.
Because it’s useful. It will come in handy. You will use it.
This is something I learned from my Dad. Years ago when Oldest was a little tyke, he cut himself. We were out and about with my Dad, and Dad pulled out his wallet and produced a Band-Aid. He told me he always kept one in his wallet, for just such an occasion. Soon after, I adopted the same habit – I had seen first-hand why this was a great idea.
You carry your wallet anyways. The Band-Aid takes up practically no measurable space, weight, or anything – it adds no burden to your daily life. And when you need it, it’s there!
The picture? I was at the gym and some bar knurling shredded my hand. Instead of bleeding everywhere, I pulled out my wallet and bandaged up. I posted that to my Instagram a couple months ago. What spurred me to write here was again at the gym, talking with the attendant at the front desk, and another patron cut herself and came up asking for a Band-Aid. I was ready to pull out my wallet if the gym didn’t have one (they did). Because, it’s useful to be prepared.
You don’t have to have a Band-Aid Brand adhesive bandage – any quality one will do. I prefer to keep the medium-to-large size ones, since you can cover a small wound with a large bandage but not really the other way around.
So the only remaining question is: why aren’t you doing this?