It’s unlikely for fleas to lay eggs in human hair. Cat fleas don’t breed on humans. In a natural setting, females can’t produce eggs on a diet of human blood. Also, fleas can only jump to the height of a person’s ankle. Once on a human, fleas quickly take a blood meal and then immediately leave. They don’t wander around.
Humans aren’t Preferred Hosts
Cat fleas don’t have host specificity. They’re capable of feeding on a large range of warm-blooded mammals, including humans. However, they do have preferred hosts, such as dogs, cats, opossums, and raccoons. Man isn’t a preferred host.
Fleas & Human Blood
Humans make poor hosts for cat fleas. A diet of human blood alone can keep fleas alive, but they’re unable to reproduce. Females only lay eggs after feeding freely for days, and doesn’t happen outside of lab conditions. Even with enough feeding, their fertility is greatly reduced on human blood.
Fleas are Poorly Adapted for Living on Humans
Fleas have co-evolved along with their primary hosts. Thus, the physical adaptations of cat fleas are well-suited for living on small mammals with dense fur. For example, their bodies are covered with backwardly-directed spines and bristles. The spination helps them attach into an animal’s hair coat, and prevents them from being dislodged.
Flea survival is largely governed by host grooming and the insects’ ability to remain on a host. Fleas have difficulty jumping onto humans without falling off due to the lack of body hair. Only 1 of 10 attempts are successful. Even if settlement occurs, fleas are easy to see against hairless human skin. They often get picked off before having a chance to feed.
Bites on Humans are Incidental
Fleas sometimes bite people who live in the same habitat as an infested animal. This typically occurs when the primary host is absent or scarce. In homes, it’s not uncommon for fleas emerging from cocoons to bite people before finding and colonizing their preferred host.
Once on the primary host of a cat or dog, adult fleas remain there. They feed, mate and lay their eggs directly on the host. In contrast, when fleas feed on people, they’ll take a blood meal and then immediately leave. Fleas don’t breed on humans. Blood meals last 4.4 minutes for males and 7.4 minutes for females.
Fleas can’t Reach Human Hair
Cat fleas can jump to a maximum height of 7.9 inches. This is as high as a person’s ankles, which is where flea bites tend to be concentrated. Fleas bite readily without roaming around. They’re unlikely to climb to a person’s pubic area, much less their head. These areas are too far from the ground (unless the person is sitting/laying on the floor, or a flea-infested pet is allowed in the person’s bed).