Mites are nasty little critters that when you find out your reptile has them, is not to be taken lightly. Mites are small external parasites that feed on the blood of your reptile. If you have one mite you have many. There are a few ways to spot if you have mites. After feeding they will turn red, or if your reptile has been soaking in it's water bowl, there maybe little pepper like floaties in the water. Those are drown mites.
If in doubt, go see your vet. It can be a serious problem if left unchecked leading to:
When dealing with mites it's important to read the directions on whatever mite killer you decide to use. Some such as Reptile Relief are meant to be used on the reptile directly, while PAM (Prevent a Mite) is meant to be used on bedding, habitat furniture, and the enclosure.