How do you know if ringworm is getting better?

When the cat scratches less and the ringworm area stops expanding, it generally means the condition is improving. You can check with a Wood’s lamp; as the green fluorescence under light gradually nears zero, the ringworm is basically cured, and you can take the cat for a pluck or scrape microscope exam.

Because ringworm is a fungal infection with a long treatment cycle, to speed recovery put an Elizabethan collar on the cat to prevent licking and scratching that spread the fungus.

Also disinfect the environment to avoid fungi in the surroundings reinfecting the cat.