UFC's Derrick Lewis Is Afraid Of Seeing Period Blood In Female Fights

UFC star Derrick Lewis says he doesn't mind watching men bleed in the Octagon -- but he gets squeamish when it comes to bloody women because it makes him think of messy periods.

The 34-year-old heavyweight spelled it all out on "Bernie & Sid in the Morning" -- saying, "I really don't like watching women fights."

When pressed on the issue, Lewis explained ... "Last week, I finally had thought I forgot they had periods. I wonder if they still fight on their period?"

Lewis continued ... "You would think they get cut in the face, something like that [and] they're bleeding and stuff like that ... but no, it's from them being on their period."

"So, I don't like watching women fight."

For the record, this has NEVER been an issue in the UFC or any other pro-MMA or combat sports organization, as far as we know.