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What Attracts Fleas to Humans?

man with face turned away from the camera reaching back to scratch his shoulder

Fleas are more than just an annoyance. They pose a health risk to both you and your pet. If you’ve used flea medication on your pet, but your pet is still scratching, you may be unwittingly attracting fleas into the environment.

Some of the other odors that humans emit can also attract fleas. On the other hand, humans are typically attracted to fleas only if they have not yet found other suitable hosts for them. Keep reading to learn about the smells that attract fleas to humans.

What Smell Are Fleas Attracted To?

Fleas are attracted to warm and stinking smells. The first and most popular idea that many people believe in is the individual variances in the chemical makeups of human skins. In other words, various skin responses and gas levels differ amongst persons based on their DNA.

Some people, for example, may create more carbon dioxide than others as a result of skin responses, which is a popular attractant for numerous blood-sucking insects and parasites, such as fleas. Aside from the chemical makeup, some individuals feel that fleas are just more attracted to some fragrances than others.

Fleas may favor a specific person based on their natural body aroma, sweat, and the goods they use on their skin, such as soaps, shower gels and deodorants. Some of the smells that are extremely attractive for fleas are discussed below.

Carbon dioxide

Gold colored bottle with a valve on top of Carbon dioxide

Besides the smell of blood, fleas are also attracted to other things, including carbon dioxide. The flea’s sense of smell is one of its strongest, and it uses it to find prospective food sources. Fleas follow their sense of smell to potential hosts when they smell carbon dioxide emitted by larger animals when they exhale.

What is the best way to get rid of fleas off of a human? Check out our post “How to Get Rid of Fleas on Humans” to learn more.

What Attracts Fleas to Humans?

Woman in a yellow shirt against a teal colored background scratching her arm

Infestations of fleas can be annoying and dangerous. In addition to warmth, food, darkness, movement, and exhaled breath, fleas are attracted to different things based on their age. Even though humans are not good hosts for most flea species, they will bite us if no other acceptable hosts are available. This is because fleas have a few fundamental survival instincts. Let’s go through these in detail.


Illustration of a thermal scan of a person

You might already know that fleas are attracted to heat but do you know why they do that? Read on to learn all the different aspects that make warmth ideal for these parasites.


Cat flea activity skyrockets in reaction to heat.  When a heated item is placed immediately in their habitat, fleas furiously leap around in random directions.


Person under a blanket asleep on a couch

Warmth attracts fleas because it represents the body heat of a possible host. They are primarily attracted to objects that are 104°F (40°C). At 122°F (50°C), there is still a significant attraction, indicating that fleas do not differentiate between hosts. This disproves the theory that fleas are drawn to the body temperature of their chosen host.

Heat alone will not attract fleas. They’ll turn towards a warm item and even sway back and forth to improve depth perception. However, they will not leap unless other cues, like air movement, are present. Flea traps that rely solely on heat as an attraction stimulus are ineffective. Similarly, adding heat to a lit flea trap does not increase performance. Thermal cues play a minor role in determining a host’s location.

Abandonment of Host

Fleas will not leave their host unless it is dying and becoming chilly. The fleas will then go to the warmest animal nearby. This can happen when dogs or cats fight and kill smaller prey animals in the wild.

The Emergence of a Cocoon

Heat and pressure cause pre-emerged adults to emerge from their cocoons. These two signs indicate that an animal is most likely lying on top of the cocoon. Warm human breath is sufficient to cause emergence. Cocooned fleas can remain inactive for five months without heat or pressure.


Children playing indoors

Movement is the second thing that fleas are attracted to. There are photoreceptors in fleas that sense changes in light, even though they do not have perfect vision. In addition to being phototactic, adult fleas move in the direction of light.

Despite their natural attraction to light, fleas are especially attracted to abrupt changes in light levels.

A change in the light level indicates a prospective host has recently passed by, casting a shadow or blocking the light.

Due to this, light-based flea traps, which are frequently used, are more effective when the light is cycled on and off intermittently.

The Odor of the Host

Woman laughing while she pinches her nose

Fleas are thought to be particularly attracted to the stench of their main host. Some species appear to be sensitive to host odor. However, there is no evidence that cat odor attracts fleas.


Adult cat fleas are drawn to light sources. Within 40 minutes of being placed in a dark room, 93 percent of the fleas will relocate to a bright area. Newly emerging adults will climb on top of things in the larval environment in natural settings. They then direct their attention to a well-lit location while waiting for a host.

Is there a bug spray to get rid of fleas on humans? Check out our post “Bug Spray for Fleas for Humans” to learn more.

Light’s Color

A lavender background with a burst of colors coming from the bottom right hand corner

Cat fleas can detect wavelengths ranging from 300 to 600 nanometers (nm). They are mainly attracted to green-yellow light with wavelengths between 500 and 530 nm. Green-yellow light attracts more fleas than regular light. Adding a green-yellow filter to lit flea traps boosts their efficacy dramatically.

Other light hues aren’t nearly as appealing. Blue and green filters offer comparable effects to natural light. Almost all other color filters—red, magenta, yellow, and medium blue—fail to generate a greater reaction than ordinary light. Cat fleas are unable to sense wavelengths exceeding 630 nm. As a result, they are the least sensitive to red light.

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Please note: We are not veterinarians and you use our advice at your own discretion. We always recommend that you consult your veterinarian whenever you have health-related conditions your furbaby is facing. With that in mind, as pet parents ourselves, we wish nothing but the best for your pet and their healthy and happy lives.