Man's best friend can be menacing and unpredictable, as 4.5 million Americans find out painfully each year.

This week diverse groups, from the Postal Service to the American Humane Association, are raising awareness about dog bites.

According to the American Veterinary Medical Association, more than 800,000 Americans receive medical attention for dog bites every year.

Half of them are kids.

Last year, the insurance industry paid out nearly half a billion dollars in claims - $484 million - up 5 percent from the previous year.

The three states taking the biggest bite: California, New York and Ohio.

Just Tuesday, in Bakersfield, California, a 4-year-old boy was riding his bike in his driveway when a neighbor's dog attacked him. The boy suffered two lacerations and needed sutures.

Related: Cameras catch family cat taking on dog that bit boy.

Surveillance cameras around the family home showed the boy's pet cat pouncing on the dog and chasing him away.

For postal workers, dogs pose an occupational hazard.

This month, the post office stopped delivery to one neighborhood in Cedar Rapids, Iowa. The reason? A particularly troublesome Chihuahua.

Today the Postal Service revealed the 30 cities where postal workers have been attacked the most.

Topping the list: Houston, Los Angeles, Cleveland, and San Diego.

Neither rain, nor hail, nor sleet, nor snow can keep these couriers from their appointed rounds. But apparently dog bites can.

Dog behavioralist Brandon Fouché said it's usually the owner's fault when a dog is prone to bite someone.

He insists common games like fetch and tug of war actually trigger a dog's aggressive instincts.

"Most of the problems we have with our dogs are learned," Fouché said. "It's a learned behavior when a dog shows aggression."

He gave the following advice to adults who come across an aggressive dog and want to avoid being bitten.

"You've gotta be big. You've gotta be bold and you've gotta be dominant in your personality when you see a dog doing something," Fouché said. "Most dogs live in a home where they're used to that and so you can fend them off just by saying, 'Hey, go home. Get out of here!'"

That's the advice for grown ups. Experts advise kids to approach dogs they don't know only at the owners permission. If attacked, they say, little kids should roll into a ball.