A. It likely is left over flea dirt from fleas prior to the first treatment. Fleas can be tricky and may take a few treatments before they go away. You can always try combing the area and seeing if it gets worse. You will also have to be sure to clean up his sleeping area and any areas in the house he goes.
Fleas have a cycle of about two weeks. Adult fleas living in your house (usually in the carpets) would lay eggs and take 10-14 days to hatch however they can lay dormant and wake up when they think there is food to feed on. They can be difficult to get rid of as you need to kill adults, wait until the next cycle starts and kill the newly hatched ones before they have time to lay eggs and breed again. This will also depend of the type of product used to treat your house. Depending where you live grocery stores and pet stores sell flea spray/powders but some will only kill actual fleas, some will also kill the eggs. You need to vacuum very well everyday )be sure to get rid of vacuum bag after), wash all bedding and treat carpets, wash floors etc. It'll take some work but you can get rid of them.
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