My cousin has a terrible toothache so I am thinking of giving her bleach for it.
Bleach isn't made for toothaches, why would you do that?
I don't know what else to do. I tried every other painkiller but it doesn't seem to work on him
Regardless of you not knowing what to do for a pain killer you do know that bleach is a cleaning chemical and not meant to be a pain killer. It's not going to help with treating the pain and it's likely going to make things even worse. Don't give people bleach to treat pain!
Needless to say, I didn't do it.
That's good! You could have seriously killed her by having her drink bleach, so I am glad that you decided not to.