What Do Fleas Look Like? The Ultimate Flea Guide.

How to identify fleas, flea eggs, and flea bites on pets and humans.

How to identify fleas, flea eggs, and flea bites on pets and humans.

Fleas can be found in your house or on your pet around the year. But, flea season usually peaks during the hot days of summer. More than 2,200 species and sub-species of fleas have been identified, but only a small number of these affect cats and dogs.

Fleas are external parasites that suck on the blood of mammals and birds. Usually, animals are their primary source of blood, but fleas can also feed on human blood. Fleas are reddish-brown in color.

Fleas differ in their host preference, their vector ability, and their degree of association with human beings. So, you need to know which species of fleas are present to choose a defense mode and suitable control methods.

Estimates say that there are about 200 genera and 1,100 species of fleas in the entire world. Another report notes that 69 genera and 318 species and subspecies were described in North America north of Mexico in 1966. There are possibly a thousand other flea species that still await discovery and description. Of the known flea species, 95 percent use mammals as their hosts, and the other 5 percent use birds.

If you see your pet scratching themselves more frequently and with greater urgency than usual, then it may be time to check them over to ensure that there are no fleas are present. If your pet has fleas, it’s likely fleas are already present inside your house, too.


What Do Fleas Look Like?

What Do Fleas Look Like?

Fleas are small, wingless insects about 2-4 mm in length with laterally compressed bodies. Fleas are incredibly tiny, which makes it difficult to notice them around your house until a large infestation is underway. The fleas’ armored bodies make it almost impossible to crush them, which helps them hide in your carpet undetected. It is also possible for fleas to hide unnoticed in upholstery.

Your pet may bring these parasites into your home. Fleas have flat bodies and strong legs, which enables them to jump long distances. They can easily move from one person or animal to another.

Fortunately, human beings will likely come across only a few flea species as pests or vectors of diseases. Still, individuals concerned with flea control should identify the common fleas that attack humans, pets, and domestic rodents.


What Do Fleas Look Like to the Human Eye?

What Do Fleas Look Like to the Human Eye

Adult fleas are visible to the human eye, but they are fast and can easily hide in your pet’s fur. They are usually brown or reddish-brown and have six legs.

To identify if an insect is a flea, you should first observe its head and thorax and determine which of the three groups the flea belongs: those with genal and pronotal combs present, those with only the pronotal combs present, or those with genal and pronotal combs absent.

The front legs of a flea are abnormally short compared to the long back legs – structured to make them one of the best jumpers in the animal kingdom. Fleas have a rubbery resin called resilin. Resilin creates a hinge where the back legs attach to the thorax. It is these resilin pads that are compressed and released when the flea crouches to jump. The energy in the resilin pads is transferred to the leg making for a spectacular leap.

A flea’s barbed stylets penetrate the host’s skin, while a long needle-like tube called the epipharynx forms a drinking tube. A flea’s mouth and guts are equipped with a pump, making it easy for them to pull blood from the host to its body.


What Does Flea Dirt Look Like?

What Does Flea Dirt Look Like?

Use a flea comb on your pet to separate the fur so you can inspect the skin. You will likely notice small, dark specks on the skin – fleas are typically brown, black, or reddish. If you see one of these dark dots move, it is probably a flea on your pet. These pests are small insects with six long legs, making it easy for them to jump from one host to another. And a single female flea can lay up to 50 eggs in a day. This problem must be tackled right away, considering that these factors make spreading easy for fleas.

As you check your pet, you will notice “flea dirt,” another term for flea excrement. Flea dirt turns reddish-brown after coming in contact with water, the red hue on a speck coming from the blood that flea had consumed.

Another telltale sign of flea infestation a flea bite on the skin of your pet. Flea bites will leave the area of the skin red and inflamed. Fleas are specifically likely to attack your pet’s hind legs, belly, neck, and ears.


What Do Fleas Look Like on Cats and Dogs?

What Do Fleas Look Like on Cats and Dogs?

Ctenocephalides felis and C. canis are the two flea species that attack cats and dogs. Both species occur in the United States. Cat fleas are more abundant and are generally more distributed than dog fleas. A cat flea’s head is twice as long as high as the dog flea’s head. And, the front margins of the heads of these two species of fleas have different shapes.

In most cat fleas, the first and second teeth of the genal comb are approximately similar in length. However, you will find that in a typical dog flea, the first tooth is shorter than the second. While you will find one stout bristle in a cat flea, a dog flea has two stout bristles between the long postmedian apical hair on the hind margin of the hind tibia.

These species are usually found inside of homes, underneath houses, or in yards. This is because fleas prefer locations in which dust and debris accumulate. These fleas will attack cats and dogs, and various other mammals such as raccoons and rats. Fleas can even cause severe and painful bites on human beings, especially during the summer. Under favorable conditions, one generation of cat fleas requires 2 to 4 days for the eggs, 8 to 24 days for the larvae, and 5 to 7 days for the pupae – meaning a cat flea grows from egg to adult in 15-35 days, depending on the conditions of their environment.


What Do Fleas Look Like on Humans?

What Do Fleas Look Like on Humans?

Pules irritans, another species of fleas, is found in the warmer parts of the world. In the United States, these fleas are found on the Pacific Coast, Middle West, and South. This flea species can attack humans and is often responsible for causing dermatitis or allergy due to flea bites. A pest infestation is particularly likely in homes, barns, barnyards, and their surrounding premises. The second species of Pulex (P. Simulans) occurs in Central and Southwestern United States and Central and South America.

Additionally, the human flea attacks a wide variety of hosts, including swine and dogs. On farms, severe infestations of fleas have been noticed in hogpens. These insects are known to survive for weeks or months, even after the hogs were carried off to the market. These fleas were even collected in areas far away from human habitation, particularly on animals like coyotes, prairie dogs, ground squirrels, and burrowing owls.

In one scientific experiment, scientists infected the human flea with the plague. They observed that the fleas were indeed capable of transmitting the bacteria in the laboratory.

The human flea is distinguished from other fleas common in the United States by the absence of the pronotal and genal combs and lack of an internal rod-like thickening on the mesopleuron. Unlike other species, the human flea has an ocular bristle inserted beneath the eye.


What Do Flea Eggs Look Like? What Do Flea Eggs Look Like?

Adult fleas will deposit eggs on a mammal’s hair coat, including the coats of any pets in your house; eggs on the hair coat of mammals quickly fall off and contaminate the environment. Or, the flea will lay eggs directly into the surrounding environment. Eggs are small (-0.5 mm), ovular, and pearly white. However, they are not always easy to identify.

Flea eggs are easy to confuse with dandruff, but there are telltale differences between the two. Dandruff appears in flat flakes in irregular shapes, while flea eggs are uniformly oval-shaped. Dandruff will stick to the pet’s fur and be hard to remove, but flea eggs are more slippery and can move from one place to another quickly.

Flea eggs hatch out into larvae that go on to live in the cracks and crevices of rugs, upholstery, carpets, blankets, floors, sand, earth. The larvae around flea pupae loosely spin a cocoon, which encases the flea pupae. Female fleas produce relatively large and sticky eggs, white in color, at a rate of about 10 to 25 in a day.

Flea eggs are also different from “flea dirt”- the digested blood that adult fleas leave as waste. This looks similar to flecks of pepper, whereas flea eggs look like salt grains. Flea dirt clumps easily and sticks to the fur of the pet. Like flea eggs, flea dirt is a signal of a flea infestation on your pet.


What is the Life Cycle of a Flea? What is the Life Cycle of a Flea?



A female flea drops her eggs indiscriminately among host fur, feathers, or directly onto the floor. In warm situations, her eggs hatch in about two to three days. The resulting flea larvae are small, legless, and worm-like. They have short antennae, mandibulate mouthparts, and rigid hairs along the body.


The larvae will hatch after 1 to 12 days, this depending on the temperature and humidity of the environment. Larvae feed on the blood from flea species, the organic debris, and the flea eggs present in their environment. Like locations with lots of shade, larvae prefer habitats that are cold and undisturbed.

Larvae will not develop in bright sunshine areas. They actively avoid light by burrowing deep into carpet fibers and organic debris. Flea larvae will molt twice, then develop into pupae in their protected environment. Moisture level in the air is of prime importance for larvae growth, and larvae typically fail to grow where the relative humidity is less than 50 percent.


In optimal environmental conditions (27 degrees Celsius and 80 percent humidity), adult fleas will begin to emerge from the pupae after approximately five days. But, pre-emerged adults can remain quiescent for weeks or months until they find a favorable environment, one that indicates the presence of a host.


After the adult fleas emerge, they need to feed within days. Fleas locate their possible hosts using visual and thermal cues. Under typical conditions, the entire flea cycle will complete in three to eight weeks.

The females will start to produce eggs within 2o to 24 hours of her initial feeding. A female flea will likely lay several hundred eggs over her approximately 50 to 100-day life span. Numerous future fleas may be developing in an environment simultaneously, no matter how many flea eggs you manage to kill.

Adult fleas will survive off the host for a short period. Some sources say that adult fleas can live up to two weeks if they do not find a new host; others state that fleas can live for two months or longer without a host.


What Do Flea Bites Look Like?

The degree of itchiness and discomfort an animal feels from flea bite allergy varies because some are allergic to fleas while others are not. Flea bite allergy, which is also called flea allergy dermatitis, flea bite dermatosis, or flea bite hypersensitivity, is a common skin condition in cats and dogs. Flea bite irritation commonly occurs when animals are allergic to one or more proteins in the flea’s saliva.

Nonallergic animals may develop mild itchiness at the flea bite site, usually only for a brief period. However, animals with flea bite allergies will develop itchiness in parts of the body away from the flea bite site. The intensity of itchiness tends to progressively worsen with continued exposure to fleas, leading to hair loss and other animal skin problems.

Even just one or two flea bites weekly may trigger and perpetuate an allergic reaction and uncontrollable itching. Animals of every age can develop a flea bite allergy, but this allergy is most common in animals between the ages of one and five. This occurs most often in the summer. But, in tropical or sub-tropical areas, allergic reactions may occur year-round since warm weather favors heightened flea production.

Evidence of adult fleas includes finding “flea dirt” (brown-black specks consisting of flea excrement containing digested blood) and flea eggs (white specks) on affected pets or other pets in the household. However, animals with an active flea bite allergy may actually have no fleas on their body at the time of examination. Often, fleas come dislodged through the pet’s excessive chewing and licking of the skin. To diagnose a flea bite allergy, your vet will conduct an intradermal skin test and a blood test.


What Do Fleas Look Like on a Dog?

What Do Fleas Look Like on a Dog?

For a dog, flea bite allergy symptoms are identifiable by scratching on the animal’s skin. The dog may experience additional damage to the skin if the allergy is more severe. The intensity of scratching can range from mild to severe and can worsen as the dog ages. The areas most often affected by the allergy are on the animal’s lower back, tail, head, hind legs, and belly.

In severe cases, the allergy may affect the pet’s entire body. The affected skin is very itchy and may show small bumps, abrasions, scratches, scabs, redness, and hair loss. Bacteria may also infect the inflamed skin.

Some dogs may develop a “hot spot” lesion (acute moist dermatitis), which is the skin most affected by the allergy. The dog’s excessive scratching, chewing, and licking of that particular area causes this patch of very inflamed, moist, hairless skin. The animal’s coat may thicken or darken from excessive scratching and chewing.


What Do Fleas Look Like on Cats?

Symptoms of flea bite allergy vary in cats. Cats may have a skin lesion pattern similar to the type in dogs detailed above. The allergy may develop small bumps and scabs around the head, neck, and belly (military dermatitis). Some cats may generate a small, round, reddish-yellow plaque (eosinophilic plaque or granuloma) on the groin area, abdomen, or the inside part of the hind legs.

The skin affected by the allergy will be very itchy. The cats may lick or chew this area excessively, which can cause hair loss. Some cats will have an asymmetric loss of hair on their mid-to-lower back and the hind legs, with no other sign of skin irritation (symmetric alopecia). Cat owners might mistake this chewing and licking of the cats’ skin as their normal grooming behavior, but the most common sign of flea bite allergy is the loss of hair from excessive licking on an area of the skin.


What Does Flea Bite Look Like on a Human? What Does Flea Bite Look Like on a Human?

The human flea is an annoying pest in several parts of the world. Contact with or the inhalation of larval exuviae can cause allergic reactions in humans. The females of chigoe invade human skin tissue, especially the skin of feet and toes. These render painful lesions that are prone to severe secondary lesions. Other fleas are intermediary hosts of tapeworm that can parasitize humans. Fleas are also vectors of the causative agents of several important zoonotic diseases such as murine typhus and plague.

Cat fleas cause a large variety of flea bites in humans as well. The cat flea is an unrelenting biter that attacks the ankle and toes, although it can affect other parts of the body. Women tend to be more affected by flea bites than men, suggesting a hormonal correlation between this species and humans.

The closely related P. simulans infests households and causes dermatitis in Northwestern America. Several other flea species bite humans, such as the dog flea, the sticktight flea, the northern rat flea, and several species of Xenopsylla, including the Oriental rat flea. The squirrel flea, Orchopeas howardi, and some bird fleas belonging to the genus Ceratophyllus, including the European chicken flea, occasionally bite humans as well.

Households harboring pets or domestic rodents and the members of nearby premises are susceptible to flea bites. Cat fleas and dog fleas will readily bite humans, particularly when flea populations are large or when pets are temporarily removed. Rodents in households can also carry fleas that will bite humans.

Fleas typically abandon dead hosts. If domestic rats die in wall voids or basements, the fleas will seek out a human host instead. Flea bites represent occupational hazards in many farms, barns, rabbit hatches, and poultry operations. The fleas in such cases may come directly from livestock or other animals attracted to food supplies.

Flea bites in humans

Flea bite dermatitis occurs in humans who have become hypersensitive to flea saliva. In sensitive individuals, flea bite sites typically develop into papules, causing a form of widespread urticaria, often with associated wheals, especially in children.

Skin scaling, hardening, and discoloration may occur in humans in severe cases. In adults, the extremities (hands and legs) are more susceptible to flea bites. In children, the entire body may become affected. Other symptoms of a flea bite in humans include rash, breaking out in hives, or swelling around the bite.

If you are allergic to fleas, your immune system may overreact to a flea bite and release an increased histamine amount. This can cause a severe allergic reaction called anaphylaxis. Anaphylaxis symptoms include intense itching, a rash or hives in various parts of the body, shortness of breath or wheezing, or swelling of the face, hands, mouth, or lips.

You must treat anaphylaxis immediately, or it can be life-threatening. Take Diphenhydramine (Benadryl) or an epinephrine injection (EpiPen) if you are having difficulty breathing.

With repeated exposure to flea bites, the hyposensitization may reduce the severity of dermatitis without any medical intervention. Corticosteroids and or desensitizing antigens can be administered to hypersensitive individuals to relieve their symptoms.

People may also become sensitized to flea feces and exoskeleton particles upon inhaling them through house dust or direct contact. Experts recognize adult fleas as the prime source of these allergens, but airborne larval exuviae are also associated with causing asthmatic symptoms in humans. Relief from these allergies may be achieved by administering a course of desensitizing antigens to the patient.

Through preventative measures, you can control fleas. You must consider several factors in eliminating fleas: elimination of adult fleas from pets, eliminating adult fleas from the environment, and preventative measures that will thwart re-infestation. The latter can reduce re-exposure or routine prophylactic treatment to kill adult fleas in the environment.


Like this article?

Share on facebook
Share on twitter
Share on linkedin
Share on pinterest

maybe later?

we'll send you a coupon code for later

Not ready to try MyPetDefense today? 
We’ll send you a coupon code in case you change your mind later.