Be careful

Cat flea

Ctenocephalides felis

Also called flea, household flea

Cat fleas are the usual fleas on both cats and dogs; their bites itch, and they can rarely pass on illnesses such as murine typhus or tapeworm.

Photo: Rupert Lees, CC BY 4.0, via iNaturalist

SizeAdults about 2–3 mm (1/12 to 1/8 inch) long.

Where in the houseLiving room, bedroom, basement, outside near the house

WhenYear-round indoors; outdoors and on pets they are most common in warm, humid months.

Check these features

Tiny, wingless, dark reddish-brown to black insect
Body flattened side to side, so it looks very thin from above
Long back legs; jumps several inches when disturbed
Row of comb-like spines on and near the head (seen with a magnifier)
Tiny black specks of flea droppings (dried blood) in pet fur or bedding

Bites and stings

Flea bites usually show up as small, red, itchy spots, most often around the ankles and lower legs, sometimes with a tiny dot in the center. Some people react strongly and others not at all. Scratching can break the skin. Rarely, fleas spread murine typhus, which causes fever, aches and sometimes a rash within about two weeks; see a doctor for fever or a spreading, painful or infected-looking bite, and mention flea or animal contact. Call 911 for trouble breathing or swelling of the face or throat.

What to do

Wash bites with soap and water and try not to scratch, since broken skin can get infected.
Check pets with a flea comb and talk to your veterinarian about a flea treatment; treat all pets in the home, and never use dog products on cats unless the label says it is safe.
Vacuum carpets, rugs, upholstered furniture, baseboards and pet resting spots often for several weeks, and empty the vacuum outside each time.
Wash pet bedding and your bedding in soapy water.
For a heavy problem that does not clear up, consider a pest professional. If you use any indoor product, follow the label.

Look-alikes

Bed bugBed bugs are flat from top to bottom, wider, and crawl rather than jump.

SpringtailSpringtails also jump but are soft, often gray or white, have antennae easy to see, live in damp spots and do not bite.

Tick nymphTick nymphs have eight legs, cannot jump and stay attached to the skin while feeding.

Why it came inside

Cat fleas live on cats, dogs and wild animals such as opossums, and lay eggs that fall into pet bedding, carpets and floor cracks. The young develop indoors, and new adults can wait in their cocoons for months, which is why people are often bitten after returning from a trip or moving into a home where pets lived.

Keep it out

Keep pets on year-round flea prevention recommended by your veterinarian.
Vacuum and wash pet bedding regularly.
Keep opossums, raccoons and rodents away by sealing gaps under porches and sheds and storing pet food and trash in sealed containers.
Avoid feeding or handling stray and wild animals.

What helps

Links go to Amazon search results so you can compare current options. As an Amazon Associate I earn from qualifying purchases. Always follow the product label.

Flea and tick prevention for pets

Ask your vet which product fits your pet. Never use a dog product on a cat.

See options on Amazon

Vacuum with a hose

Lets you remove bugs, webs and egg sacs without touching them. Empty the bag or canister outside right away.

See options on Amazon

Caulk and sealant

Silicone or siliconized acrylic caulk closes cracks around windows, pipes and baseboards. Bigger gaps need foam backer rod or expanding foam first.

See options on Amazon

Hand lens

A 10x magnifier makes small features easier to check, like eye patterns, markings or the shield on a tick.

See options on Amazon