When pets have fleas, combing out fleas, flea dirt and flea eggs is beneficial and will result in breaking the flea cycle that much faster.
When combing out fleas, make up a flat, open container of soapy water and neem oil or what ever non-toxic soap like our pet soap and dip the flea comb into the solution to drown the fleas and clean the comb between strokes. You have to be quick about it or the fleas can jump right off of the comb back onto the animal or you. You can use a tooth brush to clean the comb of fleas and knits that get stuck in the teeth. Scrub under water so the fleas and debris don't get all over you.
This will insure that eggs are not merely relocated and left to develop on and off the pet again.