A new type of therapy using feces and fake rubber hands may be able to help patients with obsessive compulsive disorder (OCD) overcome their fears of touching contaminated surfaces, according to new research.

"OCD can be an extremely debilitating condition for many people, but the treatments are not always straightforward," said Baland Jalal, a Cambridge University neuroscientist who was part of a team assessing if rubber hands could be a potential new type of exposure therapy.

Traditional exposure therapy often involves instructing OCD patients to touch contaminated surfaces, such as a toilet seat, and then to not wash their hands. It aims to help patients control their fears in a safe, managed environment but many find it too difficult and cannot even begin therapy.

The Anglo-U.S. trial involved patients having a fake hand and watching it being stroked until they developed a sensation that it was their own. The rubber hand was then smeared with feces while their real hand was dabbed with damp tissue to mimic the feeling of feces touching their skin.

The patients were asked to rate their disgust and anxiety levels, and the strength of the urge to wash their hands.

"Exposure therapy can be very stressful and so is not always effective or even feasible for many patients," said Jalal.

"If you can provide an indirect treatment that's reasonably realistic, where you contaminate a rubber hand instead of a real hand, this might provide a bridge that will allow more people to tolerate exposure therapy or even replace (it) altogether."

Obsessive compulsive disorder is a psychiatric condition that affects as many as one in 50 people worldwide. It can have a serious impact on people's lives, mental health, relationships and ability to hold down a job.

OCD comes in various types, one of which is characterized by severe contamination fears – even from touching everyday things like switches or door handles – leading to excessive washing.

Jalal said the results of the rubber hand study, which were published on Thursday in the journal Frontiers in Human Neuroscience, suggest fake hand contamination may help.

"The rubber hand illusion often makes people laugh at first, helping put them at ease," he said. "It's also straightforward and cheap compared to virtual reality, and so can easily reach patients in distress no matter where they are."