What's this sudden red spot on my cat's ear? Is it ringworm?
Thank you for including pictures of Bella's ear! It is certainly possible that it is ringworm, but she could also have an infection or an injury causing this redness. For now, I would leave it be and not touch it, and have her seen by a vet on Monday for it. The vet can use a Wood's lamp and do a fungal culture to diagnose if it is ringworm, and can prescribe treatment for it. I would keep Bella isolated from other animals in your home for now just in case she does have ringworm. Ringworm is highly contagious to other animals and humans, and I would wash your hands thoroughly after each time you touch her. The concern is that the Microsporum canis (fungal organism causing ringworm) is spread diffusely throughout a cat's entire hair coat, so you need to make sure to practice good hygiene to try to keep from getting it yourself. Should Bella have ringworm, you will need to disinfect the home as spores can live up to 10 months in the environment. I will put a link below on how to do that. Please have her seen by a vet on Monday, I hope this helps!
http://www.livestrong.com/article/49666-rid-home-ringworm/
Updated on September 23rd, 2025