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Fleas

Definition

Fleas are small insects that feed on the blood of humans, dogs, cats, and other warm-blooded animals.

Alternative Names

Pulicosis; Dog fleas; Siphonaptera

Causes

Fleas prefer to live on dogs and cats. They may also be found on humans and other warm-blooded animals.

Pet owners may not be affected by fleas until their pet has been gone for a period of time. Fleas look for other sources of food and begin to bite humans.

Symptoms

Bites often occur on the legs and places where clothes fit close to the body, such as the waist, buttocks, thighs, and lower abdomen.

Symptoms of flea bites include:

  • Small red bumps, often three bumps together, that are very itchy
  • Blisters if the person has an allergy to flea bites

Exams and Tests

Usually, a diagnosis can be made when the health care provider examines the skin where the bites are. Questions may be asked about contact with animals such as cats and dogs.

In rare cases, a skin biopsy is done to rule out other skin problems.

Treatment

You can use an over-the-counter 1% hydrocortisone cream to relieve itching. Antihistamines you take by mouth may also help with itching.

Possible Complications

Scratching can lead to a skin infection.

Fleas can carry bacteria that cause diseases in humans, such as typhus and plague. The bacteria can be transmitted to humans by flea bites.

Prevention

Prevention may not always be possible. The goal is to get rid of the fleas. This can be done by treating your home, pets, and outside areas with chemicals (pesticides). Small children should not be in the home when pesticides are being used. Birds and fish must be protected when chemicals are sprayed. Home foggers and flea collars do not always work to get rid of fleas. Always consult your veterinarian for help.

Gallery

Body louse, female and larvae
This is a magnified view of a female body louse with larvae. Lice cause itching and a characteristic excoriated skin rash (looks like a scrape). They may also transmit diseases, including relapsing fever, typhus, and trench fever. (Image courtesy of the Centers for Disease Control and Prevention.)
Flea
Different types of fleas prefer specific animals as hosts, but will infest humans if their specific hosts are unavailable. Fleas can carry plague and typhus. They are also thought to transmit several other diseases. (Image courtesy of the Centers for Disease Control and Prevention.)

References

Dinulos JGH. Infestations and bites. In: Dinulos JGH, ed. Habif’s Clinical Dermatology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 15.

James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM. Parasitic infestations, stings, and bites. In: James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM, eds. Andrews' Diseases of the Skin: Clinical Dermatology. 13th ed. Philadelphia, PA: Elsevier; 2020:chap 20.

Last reviewed November 18, 2022 by Elika Hoss, MD, Assistant Professor of Dermatology, Mayo Clinic, Scottsdale, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team..

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