LOUDON, N.H. — Dale Earnhardt Jr. has dropped out of the Sprint Cup race Sunday at New Hampshire Motor Speedway because of symptoms of a concussion.

Earnhardt was evaluated in Charlotte, North Carolina, this week and doctors did not clear him to race. Hendrick Motorsports said Thursday it had no timetable for his return.

Alex Bowman will drive in his place.

NASCAR’s most popular driver, Earnhardt was involved in a 22-car wreck in Daytona this month and also wrecked last month at Michigan International Speedway. He says he was feeling fine last week and thought the problem was allergies. When that didn’t help, he met with a neurologist.

Earlier this year, Earnhardt pledged his brain to researchers looking into the connection between concussions and traumatic brain injuries.

“I’m looking forward to treatment with the goal of getting back in the race car when the doctors say I’m ready,” Earnhardt said.

Earnhardt Jr. at least twice in his career hid concussion symptoms to avoid being removed from his car. In 2012, he sought medical attention several days after a crash at Talladega because of symptoms he knew were concussion-related. During that examination, it was determined he’d suffered two concussions in six weeks and was sidelined for two weeks of healing.