The hair loss under the neck and head of a cat is usually caused by skin diseases. The most common one is cat moss. In the early stage, scabs, dander, redness, swelling, itching, and hair loss will appear. As long as you insist on spraying every day, you will be fine. Can resume growing new hair. Feline ringworm is contagious and will spread to other parts of the cat's body, as well as to other pets or owners, so it needs to be treated immediately once discovered.