Most of us don’t spend much time thinking about socks. We slip on a pair in the morning before throwing on our shoes and heading out for the day. On those annoying occasions when we discover a hole, we simply toss that sock in the trash and grab another.

For people struggling with homelessness though, socks are a major problem. While plenty of people donate their old shirts or jackets or pants, few think to donate a brand-new pair of socks to a clothing drive. But the lack of decent footwear can lead to health problems, from infections to frostbite to diabetes-induced swelling — which, in severe cases, can necessitate amputation.

To help get socks to populations in need, Tom Costello Jr. founded the Joy of Sox, a nonprofit that collects tens of thousands of socks each year and distributes them to shelters and other aid agencies providing services to Philadelphia’s homeless population.

Costello, an adjunct professor at Montgomery County Community College and a former engineer, didn’t set out to become an advocate for the homeless. Much the opposite, in fact. “I used to be really homeless-phobic,” he admitted. “If I saw a homeless guy, I’d have to cross the street or avoid eye contact.”

Despite his trepidations, Costello eventually accompanied his wife to a local homeless shelter where she had been volunteering. While there, a volunteer podiatrist mentioned the health troubles caused by lack of socks, and Costello got the idea that donating socks would be a simple way he could continue to help. The couple returned during the holiday season. As people left the shelter, he handed out pairs of socks.

“This lady looked me in the eyes and said, ‘No one has ever given me a pair of socks before.’ Then she started to cry,” Costello recalled. “She reached out to give me a hug and, poof, that was my epiphany moment. ”

In the near-decade since that moment, the Joy of Sox has distributed nearly 350,000 pairs of socks. Costello started the nonprofit at his home in Wayne, Pa., until donations filled his garage. A benefactor eventually donated the use of a 2,500-square-foot warehouse, able to accommodate the large-scale donations sometimes delivered by clothing manufacturers alongside the smaller contributions made during sock drives at local schools.

Sometimes donations help people dealing with severe health crises, such as a man who stepped off a curb into a puddle and was forced to wear wet socks for weeks, until a doctor had to cut them off with a scalpel before gangrene set in. Just as often, donations help people take a step up, like a man who received a pair of dress socks for a job interview, to a child whose new socks stopped him from getting bullied at school for having worn the same pair every day.

The mission of Joy of Sox — a pun on the popular 1970s sex manual “The Joy of Sex” — has been taken on by other volunteers, whom Costello refers to as “sock angels.” Sami Grady started collecting socks in Milwaukee in 2015, after a Thanksgiving discussion with her family about an article she’d read online. Teaming up with her social worker aunt, she has now collected more than 12,000 pairs.

“People really appreciate having clean, dry socks,” Grady said. “It’s something that we all take for granted, but often people come through the food line and appreciate the socks even more than the meal.”