Fleas on adult cats are irritating, but on young kittens that are just 5 weeks old they can contribute to anaemia and exhaustion. A 5-week-old kitten that has fleas can be unhappy and lethargic until those fleas are removed, but removing fleas from a young kitten is significantly different than removing fleas from an adult cat.
Fill your kitchen or bathroom sink with warm water. It should be warm, but it should not burn you when you test it with your hand.
Place the kitten in the water and get it completely wet.
Wet the kitten's face and head with a small wet towel.
Take the kitten out of the bath and set it on a large towel.
Massage a small amount of dish washing detergent into its fur. Do not get soap into its eyes, but be thorough. Do not forget the ears, the neck and underneath the chin.
Submerge the kitten in water again and rinse it off. If it is not struggling too badly, hold the kitten in the water for a few more minutes, which will drown more fleas.
Remove the kitten from the water and dry it off with a dry towel.
Run a flea comb through the kitten's fur while it is still mildly damp. Regularly dunk the flea comb into a cup of hot water to kill any fleas that you manage to remove.
Repeat these steps every few days until the fleas are gone.
Having another person on hand to hold the kitten down while you wash it can be helpful. Place a very small amount of petroleum jelly at the base of the flea comb's teeth to catch any living fleas. If the problem persists, call your veterinarian and ask him to recommend a flea medication that is appropriate for young kittens.
Never use a flea treatment meant for adult cats on a kitten. These treatments essentially introduce poison into your cat's body in order to kill off fleas; the dosage is far to strong for young kittens.