I have two cats. They are indoor and outdoor. One has little sand like white in color round things that come from the back of his neck and top of head. I can feel them down in the fur. Only one cat has them. I can scratch them and they come out. They are sticky. Are they mite eggs, feces, flea larvae or eggs? When he lays down, they drop off by the dozens. I have tried dips,sprays, etc. Please help!