I managed a pet store for a few years at which point I used provent a mite that was quite a few years old. While I wasn't able to find an expiration date either I was not able to eliminate the mites with it. They came right back. That being said, once we ordered a new stock of it we got rid of them right away. I would try to get a new can if possible. Mites aren't something to take lightly. They are specific to reptiles and your other pets have no worries (unless they are reptiles )