SAN FRANCISCO (KPIX 5) — Veterinarians say there has been an uptick in flea problems with pets in San Francisco, and it’s getting harder to cure the problem.

“A flea is an incredible blood-sucking machine,” San Francisco SPCA’s Dr. Jennifer Scarlett said.

Scarlett says pet owners have many options when it comes to flea prevention.

“It is very hard to get rid of them, which is why prevention is the key,” Scarlett said.

Veterinarians are seeing that some flea medicines just aren’t getting the job done like they used to.

“We are seeing more and more of these products lasting for a smaller fraction of time.  Whether that’s resistance, or a flea load, we just aren’t sure,” Scarlett said.

Dog owner Amber Smith says her dog Bennie is flea free after switching from topical medication to an oral pill.

“He’s been good ever since,” Smith said.

Veterans say San Francisco’s mild weather year-round provides a comfortable environment for the fleas to thrive, making it even more important for pet owners to be proactive.