Fleas for Bearded Dragons
Photos from google images
Mites are very tiny and look like black/tan dots moving around on the dragon. A big indicator your dragon has mites is they start to have random tiny dots of blood appear on their skin. Mites operate much like a flea and bite and suck blood from whatever they attach to. After they ingest enough blood from your dragon they will lay thousands of eggs inside the enclosure. Dragon owner's that use loose substrates are the perfect breeding ground for eggs and hatching young mites to thrive, and these substrates often carry mites as there is no way to really clean them. There are many do-it-yourself treatments for mites but you can easily just give your dragon a very warm bath and scrub them well, especially in any crevasse of the body. Make sure to get rid of everything inside the dragons enclosure that has tiny cracks or spots mite eggs or tiny mites could hide, and clean the entire enclosure with hot water and bleach. Rinse well and do the same with all the remaining decor you decide to keep, rinse them off well with hot water. Quarantine your dragon from any pets or people for a few weeks, watching to see if any over mites appear, if this does not solve your problem, or if you do not want to clean your dragon yourself see a reptile vet immediately.