Blood-sucking leeches - used for thousands of years in medicine - now have the U.S. government’s approval as a tool for healing skin grafts or restoring circulation, regulators said on Monday.

The Food and Drug Administration approved an application from French firm Ricarimpex SAS to market leeches for medicinal purposes. The company has been breeding leeches for 150 years, the FDA said.

Doctors have used the small aquatic worms for several thousand years in the belief that bloodletting helps to cure a wide range of complaints from headaches to gout. They reached their height of medicinal use in the mid-1800s.

Today, doctors around the world use leeches to remove blood pooled under skin grafts for burn patients, or to restore circulation in blocked veins by removing pooled blood, the FDA said in a statement.

Leeches are particularly useful in surgeries to reattach body parts such as fingers or ears, Ricarimpex said on its Web site. The leeches can help restore blood flow to reconnected veins.

The FDA said it considered the leeches a medical device. The agency approved their sale after reviewing medical literature and safety data provided by Ricarimpex.

The FDA also examined information about how the leeches are fed, their environment, and the employees who handle them.