When President Donald Trump boarded Air Force One at Andrews Air Force Base for a trip to his Mar-a-Lago resort on February 2, 2018, the move was unsurprisingly met with its fair share of controversy. However, this time the controversy wasn’t as much about the president’s vacation habits, but about what appeared to be a small scar on the back of his scalp – a scar that many say proves that the president has had a cosmetic scalp-reduction procedure, something he’s been accused of both by his ex-wife, Ivana, and by author Michael Wolff in his new book “Fire and Fury.” But others aren’t so sure.

“What you can see in the picture is a line, but it’s very blurry,” says Berkeley, Michigan, plastic surgeon Dr. Bruce Chau. “It could be a scar, or it could just be part of his hair. It could be anything.”

But publications like “The Daily Beast” are quoting their own sources who say it’s likely that Trump had scalp-reduction surgery, given both the size and location of the incision and the surgery’s popularity in the 1980s and 1990s, when Trump’s ex once claimed it occurred during a legal deposition.

Though it is rarely performed today, scalp-reduction surgery was once commonly used to treat hair loss. According to Chau, the procedure involves stretching the skin of the scalp that has hair over parts of the scalp that no longer grow hair. The procedure is still used today to treat severe burns and extreme cases of alopecia.

But scar reduction is just one theory floating around out there – another theory is that the scar could be from a hair transplant surgery and not from a scalp reduction. But even that theory is just a theory, says Chau.

“The truth is, there’s really only one person who we can guarantee knows the truth, and that’s President Trump,” says Chau. “And just as it is with a private citizen, he doesn’t owe anyone an explanation for any cosmetic treatments he’s undergone – even if he is the president.”