Otodectes, Cheyletiella, Scabies, etc, ringworm and other fungal infections, allergies
to food can occur anytime in the life of a cat), bacterial skin
infections, endocrine disorders and more.
Ringworm, and some mites can be transmitted to people. Frontline does not treat mites. The topical: "Revolution" is for fleas, ticks, ear mites, and scabies, so it might be a good idea to switch to Revolution for a couple of months.