COLUMBIA — Stephanie Camp’s phone rang two or three times that first week, back in January. Those pesky allergies were acting up again — hives all over his body.

Camp worried about this when she dropped off her informally adopted son, Kelvin Rainey, at South Carolina, where he was enrolling a semester early to play tight end for the Gamecocks.

Rainey had lived with Stephanie and her husband, Jon, since he was in eighth grade. They are actually his best friend Zach’s parents, but Rainey called them Mom and Dad even before he moved in. He became, for all practical purposes, their second son, right down to Stephanie making sure there was always enough Benadryl around the house to treat his allergies.

Rainey eventually got some medicine from the football team’s doctor and settled in at USC. He graduated high school in December because he was eager to get to Columbia and learn the playbook during spring practices. And he now loves college so much that he will reluctantly return home to Yulee, Fla., next month for prom and graduation.

“I went down there for the spring (break) and it was really kind of weird,” he said. “I was like, ‘Oh, man, I’ve only been in college for two months and I’m so addicted to it that I forgot what high school felt like.’ ”

He is a fast-talking, enthusiastic kid, and it’s easy to believe him when he said, “I won’t have problems making friends” in college.

Adapting to new situations has never been a problem for Rainey, who, as he said, “got here the hard way.” He spent much of his youth living in Yulee, just north of Jacksonville, with his grandmother, Lillie Johnson, though he said he still maintains a close relationship with his biological mother, Tara Rainey.

He met Zach when they were in third grade, and soon the Camps were giving Rainey rides to football practice along with their own son. The Camps’ house is just down the road from Johnson’s trailer home, where several of Rainey’s relatives also lived, and Rainey would spend several nights at a time with the Camps.

By middle school, Rainey had a rambunctious reputation. His grades sagged. He got written up for mouthing off to teachers. One day in seventh grade, he was joking around with a classmate and tripped the kid, who fell and broke his hip. The kid’s mom wanted to press charges. Rainey’s football coach, J.T. Medley, helped him through the situation and became his legal guardian.

Rainey’s grandmother was stretched thin. Everyone in the trailer depended on her income, and it sometimes wasn’t enough to cover the electric bill. Rainey wasn’t a bad kid, Jon Camp said, but in that living situation, he was going to struggle at bettering himself.

“He wasn’t in an environment where he could study a whole lot,” Jon said. “He was just a kid that needed a little bit of direction. It just was a bad situation for him. It was hard to do the little things you need to do on a daily basis, like keeping your clothes taken care of and sleeping comfortably.”

Aware of his friend’s problems, Zach asked his parents if Rainey could move in. The Camps were torn. They loved Rainey, but they are not rich and knew this could strain them financially. Stephanie runs a preschool daycare and Jon worked in construction before losing his job in early 2011. They also have a daughter, Zoey, who is now 13.

“We were a little concerned. How are we going to feed another kid?” Stephanie said. “We were scared to death, because we were like, ‘I don’t know what we’re going to do here, but I think we can make it work.’ It just seemed like the right thing to do.”

So they did it. Rainey got the spare room, where Zoey practiced dance. Mirrors lined one wall, and the rest of the room was painted hot pink. When schools started sending him recruiting letters, he posted them on the walls, and soon there were so many that the pink disappeared.

That first year, the Camps sent out their usual Christmas card, plus their new son, whose presence surprised some folks who didn’t know Rainey had joined the family. He would have stood out anyway, but the card — which the Camps still have framed at home — must have seemed especially puzzling to some recipients because Rainey is black and the Camps are white.

At work, Stephanie met a parent who roots for USC. He raved about this local kid who had committed there. “That’s my son you’re talking about,” she said, and the man looked baffled. Cut-up that he is, Rainey enjoyed making light of the situation by referring to Stephanie and Jon as Mom and Dad while they were in public, just to see the reactions of people within earshot.

The Camps made the money work, with Stephanie cooking lots of Hamburger Helper dinners and her big extended family chipping in cash for another set of Christmas presents. And with a stable home environment, Rainey the wild middle schooler became junior prom king and such a favorite of teachers that they gave him blankets and supplies before he went to college.

Things are different now back in Yulee. At a recent family party, Stephanie thought, “It’s so quiet without Kelvin here.” He will stay at the Camp’s while home for prom and holidays, back in the old dance room. But he is too focused on football right now to even feel homesick.

In January, the Camps caravanned to USC with Medley and his wife to drop off Rainey. They hugged goodbye and cried. Stephanie didn’t think it would be so difficult, letting go of the second son she never thought she’d have.

“He sent me a really sweet text as I pulled off,” Stephanie said, “thanking us for everything we had done and saying that he’s going to miss us.”