Mites and lice are tiny parasites that like to live on dogs (and other species). They damage the skin by biting or burrowing and often cause intense irritation.
There are many different types of mite and louse, most of which can be treated by your vet. The sooner the problem is spotted, the easier it can be to treat. It’s important to contact your vet for an appointment if you think your dog has an infestation.