It is not known how long fleas live on humans, but they need a host to lay eggs. Fleas are unable to reproduce without the protection of a human’s fur and feathers. The adult flea needs about 12 hours of feeding time on a human host before it can lay its eggs. Fortunately, humans rarely have fleas on their skin for that long.
Once attached to a human, the adult flea will lay up to 40 eggs a day. After mating, the eggs will hatch after about two days. After laying eggs, the adult flea will fall off its host and land in a different part of the house. The eggs hatch within a few days of attachment and feed on the host’s blood and feces.
In the perfect conditions, fleas can live for a year or more. They need a human host to develop their life cycle, from hatching into larvae to developing into pupae. The larvae feed on organic debris for a few weeks and then move to the pupae stage where they live in a cocoon for long periods. While the adult fleas can survive without a host for a short time, their younger counterparts will continue to feed on the host’s blood for as long as they need to.
Human flea bites are an incidental effect of having an infested pet in a person’s environment. The adult flea may bite a human before it is ready to move onto its preferred host. While the bite is not harmful, it may cause an allergic reaction if it is exposed for a long enough period of time.