How to tell if it is ringworm or a scab from a fight injury?

From the photo, the cat has a round patch of hair loss with white scales and raised scabs on the surface, which is very likely caused by ringworm, a fungal skin disease that leads to round or oval hair loss. It is advised to do a Wood’s lamp exam or skin scraping to confirm.

Once fungal infection is confirmed, first clip the fur within 2–3 cm around the spot for easier medication, put on an Elizabethan collar to stop licking and spreading, then use a pet-specific antifungal skin medicine. If symptoms do not ease, take the cat to a pet hospital for a skin test and medicated bath, and check for other skin causes.