The fleas are biting hard this spring.
Experts say they're worse because of the light winter, followed by recent rains.
But they're not just bugging the pets. Owners are feeling the sting, too.
Gilbert Carrion said his dog, Charlie Brown, isn't the only one itching.
All the time he spends walking him is putting him in the path of fleas too.
"He's got some bites right there on the side, but they don't stick to him, because I continuously keep spraying him," Carrion said.
Dr. Dan Kirby, with Alamo Heights Pet Clinic, said this is one of the worst flea seasons he’s seen.
The itching and scratching fleas cause isn't the only problem they pack.
They carry diseases, transmit tape worms, and some pets can get so sick they need blood transfusions.
"We've had some that were close to needing transfusions, but we were able to catch them before hand, but you know these animals are getting very, very weak, because they're anemic," Kirby said.
He said pet parents often remember to treat their pets, but they forget about their yard.
"The fleas are not on the animals all the time. They're only on them about 10 or 15 percent of the time," Kirby said. "You can use nematodes in the yard, which are biologic control. You can use diatomaceous earth if you have the real dry yard."
Getting rid of fleas is not easy, and keeping the persistent pests away can be an ongoing struggle.