Fleas are small, wingless, dark brown insects. They can hop, jump, and move quickly through hair and feathers. Fleas are usually brought into the home by dogs, cats, or other furry pets. In order to live and reproduce, they feed off the blood of humans and animals.

A flea bite can produce a small red spot with a light-colored center on a person's skin. If an allergic reaction occurs, swelling and blisters may appear.

Many dogs and cats develop allergies to flea saliva. An animal having an allergic reaction to a flea bite will scratch or rub its skin until it becomes raw with sores.


  • Plague: A bacterial disease carried by rodents that is spread through the bite of an infected flea.
  • Tapeworm: An intestinal parasite obtained by swallowing an infected flea.
  • Murine Typhus: A disease spread by the bite of certain flea species.

The Vector Control Program routinely collects and tests fleas and blood samples from squirrels in our local mountains and campgrounds for plague. If tests come back positive, park rangers are notified, squirrel burrows may be treated for fleas, and warning signs are posted to inform the public on how to avoid fleas and protect themselves and their pets from this serious disease.

Plague Cases in San Diego County


Take preventive measures before flea season begins in spring and summer. Prevention is the best way to control flea bites. 

dog scratching behind ear

Ask your veterinarian about recommended flea products. Products used to stop the normal growth or reproduction of fleas on pets are the most safe and effective. But they must be used along with proper management and hygiene, including regular bathing and brushing.

  • Thoroughly brush your pet daily, using a fine-toothed metal flea comb
  • Drop the fleas into warm soapy water and flush them down the toilet
  • Do not use products on pets with raw skin or open sores
  • If you notice skin irritation or an allergic reaction, consult your veterinarian



  • Thoroughly vacuum floors, carpets, furniture, crevices around baseboards, cabinets, and other infested areas at least every other day; fleas like to hide in dark, low-traffic areas, often deep in carpeting below furniture 
  • Vacuum and wash pet bedding, as fleas are common where pets sleep
  • Throw away vacuum cleaner bag in a sealed plastic bag after use to prevent fleas from developing inside

Fleas live outdoors in coastal areas and places with moderate temperatures and fairly high humidity.

Outdoor sprays are only necessary for large numbers of adult fleas. Apply sprays directly in areas where pets rest such as dog houses, kennels, and under decks. Be sure to follow the label instructions carefully.

Consult your veterinarian before using chemical control. Keep your pet safe.


  (858) 694-2888




Rodent Flea photo by Olha Schedrina / The Natural History Museum