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You may actually have to dip multiple times to get rid of the problem 100%. A cat is considered contagious as long as you are seeing lesions. Even though the dip will help clear it up, it will not get rid of the problem with a single treatment. You should plan on dipping at least twice a week. Below is a link that will help provide good treatment information for you. Ringworm can be difficult to clear up, but it is possible.
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