They do clean wounds more quickly than normal treatment but this does not lead to faster healing, results of the world's first controlled clinical trial of maggot medicine showed on Friday.

Some patients also found so-called larval therapy more painful, according to the study in the British Medical Journal.

Gruesome as it sounds, maggots have a long history in medicine. Napoleon's battle surgeon was a maggot enthusiast, and they were put to work during the American Civil War and in the trenches in World War One.

More recently, medical experts have been looking again at the creatures' healing powers, including their potential to prevent dangerous infections like methicillin-resistant Staphylococcus aureus (MRSA).

To find out more, researchers at Britain's University of York recruited 267 patients with venous leg ulcers and treated them either with maggots or hydrogel, a standard wound-cleaning product.

They found no significant difference in outcomes or cost.

"It doesn't seem to be worth pursuing in this particular group of patients, if what you are aiming for is quicker healing," researcher Nicky Cullum said in a telephone interview.

Maggots may yet have advantages in some specialized areas, such as preparing patients for skin grafts, where faster wound cleaning means patients can be moved into surgery more swiftly. But establishing this will require further clinical studies.