We asked a dermatologist about the mystery marks on Trump's hands. Here's what he said.

• Donald Trump displayed mysterious red marks on his hand at a recent public appearance.
• The internet guessed that it could be caused by "hand herpes" or a hard fall.
• A dermatologist speculated that the hand marks are rashes and could be caused by many things.

Former president Donald Trump displayed mysterious red marks on his hand when he left his New York residence on Wednesday to attend E. Jean Carroll's second defamation trial.