A woman selling flowers at a popular tourist destination in Florida has slashed a teenage boy’s face with a box cutter when he refused to buy drugs from her.

Austin Blount was left with a 15-centimetre laceration down the left side of his face after Kristi Kaufman attacked him in front of his girlfriend at Clearwater Beach on Sunday night.

The father-of-two said the 36-year-old - who has previously been jailed for aggravated battery with a deadly weapon – flew into a fit of rage when he refused to buy flowers or cannabis from her.

"I turn around and next thing I know the girl hits me in the face with a box cutter or some type of knife and just drags it down my face," he told CNN.

"I felt a whole bunch of blood just go running down my face and I felt it and I was like, 'Oh man, she sliced me open.'"

Mr Blount said the cut went all the way to the bone and required 17 stitches.

Kaufman fled but a bleeding Mr Blount gave chase, flagging down a police officer on the bustling pier.

"He asked me what was going on. I looked at him and said, 'She just cut my face open.'"

"If she would've just cut me down here or a little bit farther I could've, I could've been killed."

Kaufman was arrested.

Mr Blount said he has no health insurance and has accrued more than $18,500 in hospital bills.

Doctors told him he will need plastic surgery to minimise the appearance of the scar on his face but Mr Blount said he will struggle to afford it.