With a name that is often misleading, ringworm--which is not caused by a worm--is a highly contagious fungus that affects dogs, cats and humans. Known for its signature circular, hairless lesions, ringworm in a dog is typically treated with creams, ointment or systemic medications. There are a few ways to tell when ringworm is no longer active on a dog.
Things You'll Need
- Blacklight
- Hemostats
- Tweezers
- Fungal culture
- Rubber gloves
Instructions
Hold a blacklight, also called a Woods lamp, over the ringworm lesions. According to the veterinarian-run website Pet Education, in some cases ringworm will glow a fluorescent yellow color if active. However, more than half of the ringworm species will not fluoresce. If the lesion glows, it is likely still active. If the lesion does not respond to the blacklight, try another method to verify the ringworm is not active.
Pluck a few hairs from the lesions with a hemostat or tweezers. Obtain hairs from each suspected lesion and try to collect scales from the lesions in the hair, as well.
Place the collected hairs in the medium of a fungal culture, as suggested by Pet Education. Place the cap on the culture but do not shut it all the way, as some air should enter the culture jar. Allow the culture to germinate for a few days, according to the culture's instructions, then check the medium. If the ringworm is still active, fungus will grow on the medium or turn red in some cases, depending upon which brand you use.