@Ben_StKilda, Thought I might explain more fully. The mite species we were talking about is a dark, dot-sized ecto-parasite that infests snakes and used to be called the Snake Mite. However, it has on rare occasions been found on lizards, and so is now often referred to as the Reptile Mite. A shame really, because it can create confusion with the other common mite species occurring on many lizards, which are not nasty. At least the latter are readily distinguished by their orange or red colouration.
When done as it should be, getting rid of mite is NOT at all harmful to a snake.
However, if a snake with mites has been kept in an enclosure, then it is a
very laborious task to get rid of them. Unfortunately these critters are like aphids where females can lay eggs and build up the population without a male. They are also very mobile and given to spreading out.
One final point. If you have any suspicions that a snake you have purchased may have mite and don’t feel confident in assessing lifted scales etc., then place it in a tub in a shallow bath (tepid - not warm or cold) for half an hour. The mite drown and if present will be evident as small blackish dots in the water. Examination under low magnification will reveal the legs if they are mite.