The evaluation was standard operating procedure after such a hit. An Eagles spokesman said later that Asomugha does not have concussion symptoms yet.
Asomugha, signed as a free agent last year after spending his first eight seasons with Oakland, was also left with a lacerated lip and sore neck as a result of the mid-air collision, which occurred on a pass play during a seven-on-seven period.
Quarterback Michael Vick attempted to hit wide receiver DeSean Jackson near the left sideline, but Asomugha and Allen, a third-year safety, converged as onlooking fans gasped.
"Just one of those plays," Allen said. "It happens sometimes. His helmet went into my chest and my forearm caught him a little bit. It happened so fast, it's hard to tell what hit what."
Allen remained on the ground for a few minutes, coughing. But ultimately he was able to continue practicing.
"I felt fine," he said. "I just had to get myself back together. As soon as it happened, it knocked the wind out of me and I laid there a little bit, and kind of felt around and made sure everything was in one piece."
Asomugha remained face-down and motionless as team trainers came to his aid and several teammates knelt around him. An Eagles spokesman said he never lost consciousness, but it was several minutes before he was able to regain his feet. He then made his way to a nearby cart and was driven to a fieldhouse adjacent to the practice field, where he was evaluated.
Asomugha, named to three Pro Bowls while with the Raiders, had 48 tackles and three interceptions in his first year with the Eagles.
The Eagles will meet New England next Monday on 6abc.