Ilza Padua bathes her 500-pound ex-boyfriend in exchange for a shower, or a $10 bill she could use to buy a bag of heroin.

Homeless for years in the madness and squalor of West Kensington, Padua, 46, is weary and nearly toothless, her leathery skin marred with scars from knife attacks and repeated spikings from dope needles.

She carries a clutch of novels with her - Robin Cook is popular among the homeless for some reason - and has survived by staying awake at night and prostituting herself only to men who seem safe. "Doctors and lawyers are OK," she said.

An astute observer, Padua says Kensington has been getting crowded lately with more homeless people flooding the neighborhood, known as the epicenter of drug crime in Philadelphia.

"There are so many kids here now," Padua said. "I ran into my 23-year-old nephew doing heroin."

The change is conspicuous: "Homelessness in Kensington is increasing exponentially," said Jose Benitez, executive director of Prevention Point, a neighborhood needle-exchange program that provides free medical clinics and accepts mail for the homeless.

What's driving the rise in homelessness is a complex mix of factors, including the pull of heroin; cuts to food stamps, General Assistance, and drug-treatment programs; gentrification in nearby Fishtown; and increased poverty.

In Kensington, the sidewalks are mottled, as though ambient filth melded with the concrete. It's not just that the sidewalks are dirty; dirt is ground into the sidewalk.

Homeless people gather near freight tracks and under bridges like hobos during the Depression. Their encampments are both convivial and dangerous, as "dope-sick" people (suffering withdrawal) turn on one another in a second, clawing for cash.

At St. Francis Inn, a Catholic soup kitchen, meals are served to the homeless, and one morning, a crowd gathered for breakfast. The vast majority of street homeless are either addicts or mentally disturbed, experts say, and people suffering from both diseases met beneath pink crape myrtle.

For a moment, folks seemed serene. Then the meal ended, and they dispersed into the street.

Though greater numbers of homeless people live in Center City, Kensington is where the largest growth in homelessness in the city has been in the last year, said Sister Mary Scullion, who runs the homeless advocacy group Project HOME.

Agency figures show average summer and winter street counts of homeless people in Kensington rose from 13 in 2010 to 158 in 2013. By contrast, the average street count in Center City in 2013 was 375, compared with 359 in 2010.

Typically, homeless numbers are wildly variable. Street counts are censuses taken on a single day, and experts acknowledge many homeless people who often burrow under bridges or take refuge in abandoned buildings are missed.

There's never been a street count of homeless larger than 900 in Philadelphia, but between 5,000 and 6,000 people have contact with homeless street outreach workers during the year, said Marcella Maguire, a director at the city's Department of Behavioral Health and Intellectual Disability Services. And, she added, the number of people in city homeless shelters ranges between 10,000 and 20,000.

Though any tally of the Kensington homeless is imprecise, the more than tenfold increase in population within three years is nevertheless staggering, experts agree.

Heroin plays a part.

Because new laws restrict prescriptions for opioids such as oxycodone (found in Percocet), young people accustomed to abusing the drug are replacing it with injectable heroin, said Philippe Bourgois, a University of Pennsylvania anthropologist and expert on the drug trade. Bourgois lived in Kensington for his research.

"Young people find themselves forced to go for the cheaper, more plentiful powder heroin you have to inject," Bourgois said.

"And these are the people who end up homeless, because addicts become trapped right around the sites where they buy their drugs and sell themselves for drug money. They call it 'getting lost in the Bermuda Triangle.' "

Traditionally, heroin is a drug of choice among white people, Bourgois said, and therefore, Kensington, populated largely by Puerto Rican residents, is undergoing an influx of young whites.

Janna Sellers, a 30-year-old former dog groomer from Northeast Philadelphia who is white, fell into homelessness in Kensington after smoking and sniffing heroin.

"I tried it, wanting to see what it was all about," she said, adding that she became hooked. "Heroin doesn't discriminate."

Maintaining an addiction can be more rigorous than work, and, soon enough, Sellers lost her job and became a denizen of the Kensington streets. She started living in a park and then a shed in Kensington. Now in treatment, Sellers said, "I want to be married and have kids. I'd like to live my life right."

Until 2012, many people with drug problems in Kensington like Sellers could afford rooms in buildings or small apartments using General Assistance dollars, Benitez said. But the state cut GA, ending that lifeline for 37,000 Philadelphians, Benitez said.

He added that when GA existed, recovering addicts contributed their stipend to halfway houses that aided recovery. But the end of GA meant many such halfway houses had to close, dumping more homeless on the streets, Benitez said.

On top of that, the state and federal governments have cut about $6 million from the city's drug- and alcohol-recovery programs over the last six years, according to Roland Lamb, director of the Office of Addiction Services in the city Department of Behavioral Health and Intellectual Disability Services.

Those cuts contribute to homelessness in Kensington, Benitez said.

The slashing of federal food-stamp benefits hastens homelessness, experts say, especially in Kensington, already the poorest area in the poorest big city in America. In Kensington, jobs other than drug dealing are scarce.

Benitez added that the larger population of homeless in Center City get greater attention from the city than Kensington. With more frequent contact from outreach services, those homeless people are placed on lists that prioritize them for housing and other programs.

"But if I'm homeless in Kensington, I may never have contact with an outreach team," Benitez said.

Further complicating matters is the dearth of homeless shelters in Kensington, he added.

Kensington is receiving more homeless people also because places like Fishtown are gentrifying, driving up rents in the area and forcing those who can't afford them to live on the streets, said Karen Pushaw, part of the team that runs the St. Francis Inn.

"Rents are up from $500 to $700 even in areas where buildings haven't been improved," she said.

Monitoring the rise in homelessness in Kensington, Maguire said, the city is trying to offer assistance. But she acknowledged, "We are overwhelmed by the numbers. It's a really big concentration of folks needing help."