A. There are 2 tests for ringworm. One is to put a fluorescent lamp (called a Wood's lamp) on the lesions in a dark room. Many species (about 50% of them) of ringworm will glow an apple green under this light. The other is to do a fungal culture, in which hairs from the lesions are implanted in a special medium to see if the ringworm fungus grows.
Actually, it's pretty unlikely that your dog has ringworm, unless you think he's been exposed to it from another animal. Most adult animals have a robust immune system that can fend off ringworm pretty easily anyways.
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