Scientists say the condition stems from sensory overload.
"The concert, overall, exceeded every expectation that you could've imagined to have," said Jenna Tocatlan, who attended a show that was part of the pop star's sold-out Eras Tour. "It's just overwhelming in the best way."
Some Swifties have taken to social media, saying the experience was so spectacular that they have shaken off some memories of the show.
"It's actually a neurologic phenomenon that can happen in any heightened emotional state," said Dr. Leah Croll, a neurologist at Temple University. "As Taylor Swift fans are going to this concert, there's so much to be excited about, there's so much stimuli to process for the brain, and that can actually get in the way of forming and storing memories of that concert experience."
Some Taylor Swift fans wearing adult diapers to her concerts so they don't miss any songs
Tocatlan said she has spoken with people who had similar experiences.
"'Like, oh, that was too good to be true -- I definitely don't remember that,'" she said.
To have something like post-concert amnesia "is really not such a bad thing," Croll said. "What it means is that your brain was so present in that moment -- that there was so much good, fun, exciting stimuli for your brain to process -- that it just didn't have the energy to focus on memory formation in that moment."
ABC News contributed to this report.