Article

Flea Bites on Humans: What They Look Like, Causes, Symptoms, and Treatment
February 01, 201901,530

What are fleas?

Fleas are an order of parasitic insects.1

Born from eggs laid on host hairs or on the ground, fleas are initially born as larvae. Small, white, worm-like animals, they survive on bits of organic material (often flea feces).1

After growing for a few days or weeks, larvae spin a small cocoon and eventually emerge as an adult flea.1

Adult fleas are easily recognized by their unique body shape. They have dark, flattened bodies, long legs, small antenna, and no wings. To make up for not having wings, fleas have become excellent jumpers, and may span distances over 150 times their own body length.1

They are small animals. Adults range in size from 2-10 millimeters.1 That is approximately the size of an ant.2

Adult fleas are the parasitic stage of the flea life cycle. Both male and female adult fleas survive on the blood of a host animal.1

 


Figure 1: Photo of an adult flea

(iStockphoto.com/3drenderings)

 

Types of fleas

There are 16 families of fleas, containing over 2,500 individual species.1

Fleas are classified by the shape and structure of their genitalia, and the number, type and distribution of spikes and hairs on their bodies.1

They may also be classified by their preferred host animals.1

Though fleas almost never feed on a single species of animal, many seem to have a preference for groups of closely related animals.1

Around 75 percent of fleas prefer to feed on rodents.  An additional 20 percent prefer marsupials, bats or birds. No flea specifically targets humans.1

Since most species of fleas live on animals and in areas far away from humans, we never come into contact with them.1

A few hundred species of fleas worldwide are believed to come into regular contact with humans. Of those, only a few are considered medically important for their ability to bite humans, and transmit diseases.1

Human flea

The “human flea” gets its name from how often it is found in and around human homes. It does not really target humans, but happens to prey on lots of animals humans like to live near. This includes cats, dogs, guinea pigs, rats and goats.1

Cat flea

The cat flea is the most common flea found in human homes. It preys on cats and dogs, but can also live on possums, raccoons and rats. Though there are “dog fleas”, most dogs who have fleas actually have cat fleas.1

Oriental rat flea

Oriental flea rats are found on rats in warm and temperate regions. It is believed to be the main species of flea able to transfer the bacteria that causes the plague from rats to humans. It may also transfer some forms of typhus and parasitic worms.1

Northern rat flea

The norther rat flea lives in cooler, temperate regions. In addition to living on rats, it has been known to live on voles, mice, and ground squirrels. It is not believed to be able to readily infect humans with plague. It has, however, been shown to transfer other bacteria, such as S. enteriditis and F. tularensis, and blood parasites.1

Sticktight flea

The sticktight flea gets its name from its females, who have the habit of using their mouthpieces to grab on to skin and stay attached for multiple days. They do this to keep from being brushed off while waiting to be ready to lay eggs.

Sticktight fleas may infest birds, dogs, cats, rats and other rodents.

Sand flea        

Sand fleas, also called jiggers or chigoes, live in sand or loose soil. They are poor jumpers and usually latch on to the feet of a host animal as it walks over them. Host animals include dogs, pigs, cows, or humans.1

Sand fleas feed differently than other fleas. While most fleas bite and feed briefly and then jump away (see below), female sand fleas burrow their entire head into the skin of their host. They stay there, feeding and growing, until they are ready to lay their eggs. This may last up to about 3 weeks. They may grow up to about the size of a pea.1

Since sand fleas stay attached for so long, and create larger wounds than other fleas, being bitten by sand fleas is associated with a greater risk of secondary infection. Sand flea bites have been known to become infected with1:

  • Tetanus
  • Streptococci bacteria
  • Staphylococci bacteria
  • coli

They may also progress to gangrene.1

Infection with hundreds of sand fleas can lead to honeycomb-like holes in the affected skin.1

 

What are flea bites?

The flea bites you see on your skin after a flea has bitten you are not actually caused by the bites themselves. Rather, they are caused by your own immune system reacting to proteins from the flea’s saliva that entered the skin while the flea was eating.3,4

How do fleas bite?

Unlike many other “biting” insects, who pierce skin with a single needle-like mouth piece, fleas really “bite”.5

They have two opposing mouth pieces, called laciniae. Though they are vertical, not horizontal like our jaws, they work similarly. They are lined with teeth and the flea closes them down on the skin, making a hole.5

When the hole reaches a small blood vessel, it sticks another, needle-like mouth piece through its wall so it can suck up blood as it flows by.5

Throughout the biting process, the flea secretes saliva from its laciniae that contain proteins which work to4:

  • Prevent the blood from clotting
  • Prevent the host from feeling the bite and scratching the flea off
  • Preventing the animal’s immune system from effectively attacking the flea

When the flea is full, it simply pulls the needle-like mouth piece out of the blood vessel and jumps away.5

How does flea saliva cause a flea bite?

When your body is exposed to flea saliva the first time, you will probably experience no symptoms. Your immune system, though, recognizes there are foreign proteins in your skin and blood and begins creating special kinds of antibodies called IgE and IgG antibodies.3,4,6

When another flea bites you later, the IgE and IgG antibodies can bind to proteins in the flea’s saliva and trigger an immediate immune response.3,4,6

Activated IgE and IgG antibodies tell specialized white blood cells called mast cells to release a ton of protective chemicals. These chemicals include4:

  • Histamine
  • Tryptase
  • Leukotrienes

These chemicals, in turn, cause the symptoms of the flea bite on the skin: redness, swelling, itching and tenderness or pain.4

 

What do flea bites look like on humans?

At first, flea bites often look like small puncture marks. Within 5 to 30 minutes of a bite the area around the bite begins to swell and itch.1

Usually, the bite becomes hard and turns red within 12 to 24 hours.1 The bites are usually several millimeters across (2-10).7

The skin reaction usually lasts at least a week.1 There have been reports, however, of skin reactions from bites lasting up to 2 years.7

There is usually more than one bite because individual fleas bite multiple times before finishing a meal.1

 


Figure 2: Flea bites on a human ankle

(iStock.com/anamariategzes)

 

How can you get flea bites?

You can get flea bites by coming into contact with adult fleas.1

Usually, humans come into contact with fleas by spending time near animals or near common resting places of animals that are infested with fleas. This is most often the family pet, but may also be livestock, rats or even wild animals.1,8

What are the symptoms of flea bites?

If you’ve been bitten by fleas, you’ll likely have:

  • Multiple bites clustered together, primarily on your feet, ankles or legs1,7
  • Bites that start as swollen bumps that become red, firm and pimple-like within a day1
  • Bites with red puncture marks in the middle1,7
  • Intense itching that may be worse at night7
  • Tenderness or pain in or around the bites7

 

Flea transmitted diseases

If the flea that bit you was carrying a bacterial, viral or parasitic infection, you may experience additional symptoms.

Three of the most important flea-transmitted diseases, and their symptoms, are discussed below.

Murine Typhus

Murine Typhus is caused by the bacterium R. typhi. It is transmitted from rats to humans by fleas, usually the oriental rat flea.1

Symptoms usually take 6-14 days to appear after the flea bite.1

Symptoms include1:

  • High fever
  • Headache
  • Chills
  • Nausea
  • Muscle pain
  • Weakness
  • Wide spread rash, frequently on the belly or back

Doctors treat Murine Typhus with antibiotics. Common antibiotics prescribed include tetracycline, doxycycline and fluoroquinolone.1

Flea-borne Spotted Fever

Flea-borne Spotted Fever is caused by the bacterium R. felis. It is carried by cat fleas.1

Most cases of Flea-borne Spotted Fever have been reported in hot environments, but there have been cases reported in the more temperate Europe and northern United States, as well.1

Symptoms of Flea-borne Spotted Fever include1:

  • Fever
  • Headache
  • Rash
  • Fatigue
  • Muscle pain
  • Eye-sensitivity to light
  • Reddening of the whites of the eyes
  • Abdominal pain
  • Diarrhea
  • Vomiting
  • Small, isolated black marks or wounds on the skin

Flea-borne Spotted Fever is treated with antibiotics, often doxycycline.1

Plague

The plague is caused by the bacterium Y. pestis. Y. pestis lives in rodents and can be transferred by fleas to humans. Many different species of fleas are believed to be able to infect humans with the plague.1

Symptoms of plague begin 2-6 days after infection and may include9:

  • Dizziness
  • High fever
  • Feeling extremely unwell and needing to lay down
  • Extreme swelling of one or more lymph nodes in the groin, armpit or near the neck

If left untreated, symptoms may progress to9:

  • Swelling in the brain (meningitis)
  • Chest pain and cough (pneumonia)

Sometimes, the disease starts with pneumonia, skipping the “bubonic” stage.9

Without treatment, plague may be fatal in up to 50-90 percent of cases. Leaving plague that is affecting the lungs or brain untreated is almost always fatal.9

The treatment for plague is high doses of antibiotics. Commonly, doctors chose to use streptomycin, though doxycycline or gentamicin may be given as well.9

If you experience any of the symptoms of Murine Typhus, Flea-borne Spotted Fever or the plague after having been bitten by a flea, please seek medical attention immediately.

This is by no means an exhaustive list of flea-transmitted diseases. If you had symptoms of flea bites you began experiencing any abnormal or concerning symptoms within about 2 weeks, please seek medical attention as soon as possible.

 

Flea bites or something else?

Flea bites may look similar to the bites of other bugs, but there are some characteristics that may help you determine if you were likely bitten by a flea, or another insect.

 

Flea Bites vs. Bed Bug Bites

Like flea bites, bedbug bites often appear clustered together. They may also have a puncture mark in the center of the bite.10

While flea bites are most likely to appear on the feet or legs, bed bug bites usually appear on skin in areas that spend much of the night in direct contact with the bed.7,10

Bedbug bites are more likely if they appeared within 11 days after having slept in a strange bed.10

 


Figure 3: Bed bug bites on human back

(iStock.com/jcarillet)

 

Flea Bites vs. Mosquito Bites

Similarly to flea bites, mosquito bites are caused by an allergic reaction to mosquito saliva.8

Mosquito bites may look different, depending on how your immune system responds to the saliva. They may appear very similar to flea bites, as hard, red pimple-like bumps or more wheal like. They may also first appear as a wheal and then slowly turn red and hard over the course of day or so.8

Mosquito bites are more likely than flea bites if you have been outdoors where mosquitos are likely to have been present, and if you have not been in contact with animals.

 


Figure 4: Mosquito bites on human neck.

(iStock.com/dimid_86)

 

Flea Bites vs. Scabies

Scabies is caused by a type of mite called S. scabiei. Unlike fleas, these mites live their whole lives on humans, and the females burrow into human skin.11

Most cases are contracted from skin-to-skin contact with another person who has scabies.11

A combination of the burrowing process and an immune reaction to the mites causes a rash on the skin. The rash is extremely itchy and occurs in the webbing between the fingers, on the inside of the wrists and elbows, in the armpits, on the genitals or buttocks, or the breasts in women.11

You are more likely to have scabies if your rash developed after contact with someone who had an itchy rash and you have not been in contact with animals that might have been infested with fleas.1,11

 

Figure 5: Scabies on a human hand

Acarodermatitis Hand” by Sven Teschke is licensed under CC 3.0.

 

Flea Bites vs. Chigger Bites

Chiggers are the larvae of certain types of mites. Chiggers are parasitic feeders, but they eat skin tissue, not blood.12,13

Chiggers hatch from eggs in the soil in warm, humid weather. You are likely to come into contact with chiggers during outdoor activities in the summer or early autumn in or around thick vegetation. These may include: camping, hiking, rafting or farm work.12,13

Unlike flea bites, chigger bites usually do not appear in a pattern or have a puncture mark in the center. They are likely to be found on frequently exposed skin. Chigger bites may appear on the arms or hands, feet or ankles, or near the groin, abdomen, armpits, pant-line and/or sock-line.12,13

Chigger bites usually begin itching within hours of the bug attaching.12

A good sign that your bug bites might from chiggers is that they appeared 3-24 hours after outdoor activities in areas that might have had chiggers.

 

Figure 6: Chigger bites on foot and ankle.

Bites on a foot from the Harvest mite Trombicula alfreddugesi

by  TimVickers is licensed under CC0 1.0.

 

Diagnosis of Flea Bites

The first step in diagnosing flea bites is examination of your skin reaction. If the reaction is consistent with possibly being from flea bites, your doctor will likely ask you to search for evidence of fleas  where you believe you were bitten.8

If you are able to find8:

  • Live fleas
  • Flea feces in your home or on a domesticated animal
  • Bites on a domesticated animal

your diagnosis will be confirmed.

 

Treatment of Flea Bites

The actual treatment of flea bites is the elimination of the fleas.8

If you do not have a pet, you may need to identify the animal carrying the fleas. This may be a rodent or other animal living in your house. Removing them may help decrease the flea population.1

Fleas from wild animals may contaminate outdoor areas. These fleas may be kept under control using insecticides.1

If your pet has fleas, they will need to be treated for fleas to eliminate your bites.1,8

Pets may be treated with a variety of oral and topical insecticides, such as14:

  • Selamectin
  • Fipronil
  • Imidacloprid
  • Nitenpyram
  • Permethrin
  • Pyriproxyfen
  • Lufenuron

You should see your veterinarian to make sure you get the right medication for your pet.1

You should also wash all pet bedding and vacuum carpets in the areas where your pet likes to rest to help eliminate flea eggs.1

Treating the symptoms of flea bites in humans

Uncomplicated flea bites usually do not require much treatment.

To manage the intense itching, your doctor may recommend using an anti-itch cream, such as hydrocortisone cream.7

This improves your quality of life and helps prevent secondary infections caused by scratching.7

If you have developed a secondary infection from scratching your bites, or if you contracted a flea-transmitted infection, you will need antibiotics.1 Which antibiotic your doctor prescribes will depend on the exact bacteria and the severity of your symptoms.

 

How do you prevent flea bites?

You can prevent flea bites by avoiding contact with adult fleas.1,8

This may mean1,8:

  • Avoiding contact with possibly infested animals
  • Preventing rodents or other wild animals from living in or near your home
  • Protecting pets from flea infestations with appropriate medications

 

Flea Bites FAQs

How big are fleas?

Fleas are very small. Adult fleas range in size from 2-10 millimeters, approximately the same size as an ant.1,2

Can you feel flea bites and what do flea bites feel like?

You usually don’t notice the bite itself, which is why fleas are able to bite you multiple times in one feeding.1

Once your immune system reacts to the flea’s saliva, however, you will most likely notice intense itching at the site.1 This may be accompanied by tenderness or pain.7

On the skin, flea bites feel like small, hardened bumps.1

Do flea bites itch?

Flea bites almost always itch. The immune system releases chemicals, such as histamine, in response to a flea bite, which cause intense itching.4

Why do flea bites itch so much?

The immune system releases chemicals, such as histamine, in response to a flea bite, which cause intense itching.4

How long do flea bites last?

Flea bites usually last around a week.4 They may, however, last significantly longer in people who are very allergic. Some bites have been known to last up to 2 years.7

Can humans get fleas from dogs?

Yes. In fact, the main way humans are exposed to fleas is from contact with infested pets.1,8

What does a flea bite look like on a dog?

Flea bites on a dog’s skin appear similar to flea bites on human skin. They will likely look like red, raised, pimple-like bumps on the dog’s skin.8

My flea bites marks won’t go away. How do I get rid of flea bites scars?

Scarring after an inflammatory reaction, like a flea bite, is called “post-inflammatory hyperpigmentation.”15

Treatments that may fade these marks include15:

  • Hydroquinone
  • Azelaic acid
  • Retinoids
  • Glycolic acid peels
  • Laser therapy

You should visit your dermatologist to determine which treatment option is best for you.

Can my pet’s fleas lay eggs in human hair?

If your cat or dog has fleas, they almost certainly have “cat fleas”. Cat fleas can bite humans, but they cannot live and reproduce  or lay eggs on humans.16

 

References

  1. Bitam I, Dittmar K, Parola P, Whiting MF, Raoult D. Fleas and flea-borne diseases. International Journal of Infectious Diseases. 2010;14(8):e667-e676.Doi: https://doi.org/10.1016/j.ijid.2009.11.011
  2. Department of Energy. The Scale of Things — Nanometers and More. June 25, 2006. Available at: https://science.energy.gov/bes/community-resources/scale-of-things-chart/. Accessed September 1, 2017. PDF.
  3. Cuellar A, Rodriguez A, Halpert E, et al. Specific pattern of flea antigen recognition by igG subclass and IgE during the progression of papular urticaria caused by flea bite. Allergologia et immunopathologia. 2010;38(4):197-202. Doi: 10.1016/j.aller.2009.09.012
  4. Ribeiro JMC, Arca B. From sialomes to the sialoverse: an insight into salivary potion of blood-feeding insects. Advances in Insect Physiology. 2009;37:59-118.Doi: 10.1016/S0065-2806(09)37002-2
  5. Krenn HW, Aspöck H. Form, function and evolution of the mouth parts of blood-feeding Arthropoda. Arthropod Structure & Development. 2012;41(2):101-118.Doi: 10.1016/j.asd.2011.12.001
  6. Garcia E, Halpert E, Rodriguez A, Andrade R, Fiorentino S, Garcia C. Immune and histopathologic examination of flea bite-induced papular urticaria. Annals of Allergy, Asthma & Immunology. 2004;92(4):446-452. Doi: https://doi.org/10.1016/S1081-1206(10)61781-4
  7. Youssefi MR, Ebrahimpour S, Rezaei M, Ahmadpour E, Rakhshanpour A, Rahimi MT. Dermatitis caused by Ctenocephalides felis (cat flea) in human. Caspian Journal of Internal Medicine. 2014;5(4):248-250. https://www.ncbi.nlm.nih.gov/pmc/articles /PMC4247491/.
  8. Singh S, Mann BK. Insect bite reaction. Indian Journal of Dermatology, Venereology and Leprology. 2013;79(2):151-164. Doi: 10.4103/0378-6323.107629
  9. Prentice MB, Rahalison L. Plague. Lancet. 2007;369(9568):1196-1207.Doi: 10.1016/S0140-6736(07)60566-2
  10. Bernardeschi c, Le Cleach L, Delaunay P, Chosidow O. Bed bug infestation. BMJ. 2013;346(138):1-8. Doi: 10.1136/bmj.f138
  11. Chosidow O. Scabies. New England Journal of Medicine. 2006;354:1718-1727.Doi: 10.1056/NEJMcp052784
  12. Santibanez P, Palomar A. The role of chiggers as human pathogens. An Overview of Tropical Diseases. 2015:173-202. Doi: 10.5772/61978.
  13. Sharma P, Kakkar R, Kaore S, Yadav V, Sharma R. Geographical distribution, effect of season and life cycle of scrub typhus. JK Science. 2010;12(2):63-64.
    https://www.jkscience.org
  14. Rust MK. Advances in teh control of Ctenocephalides felis (cat flea) on cats and dogs. Trends in Parasitology. 2005;21(5):232-236. Doi: 10.1016/j.pt.2005.03.010
  15. Plensdorf S, Martinez J. Common pigmentation disorders. American Family Physician. 2009;79(2):109-116. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.729.5959&rep=rep1&type=pdf.
  16. Nazarko L. Flea bites: diagnosis, treatment and prevention. British Journal of Healthcare Assistants. 2010;4(9):442-444. http://web.b.ebscohost.com

Comments

No comments

New Articles

Experts notesMedicine
Open source health care resources.
June 25, 201901,709

These changes mirror and support organizational changes in the health care industry. Whether...

Experts notesMedicine
Openhealth — Open source software in health care.
June 25, 201901,381

Around the world, health care software is moving from hospital-centered departmental systems, to...