London: The itch-scratch relationship is said to be one of the human body's great biological mysteries. Now, scientists have claimed that itch is felt most intensely at the ankle which is also the best place to scratch.

A new study by Liverpool John Moores University says that ankle is the most satisfying spot to scratch and it even beats hard-to-reach parts of the back, an agency reported.

For the study, the scientists recruited some healthy male and female volunteers, aged 22 to 59. The subjects were made to itch by rubbing them with cowhage, a plant with tiny hairs that irritate the skin.

The itches were induced on three parts of the body -- forearm, ankle and back. For five minutes, participants were asked not to scratch, instead told to record how itchy they felt at each spot, a daily reported.

Then the scientists scratched each location themselves with a laboratory brush and asked the volunteers exactly how pleasurable the sensation was.

On comparison of the sensation of scratching on different areas of the skin in the three parts of the body, the findings revealed that the itch was felt most intensely at the ankle.

And, ankle was also the spot where pleasure of scratching was felt most keenly and persisted longest, say the scientists.

By contrast, the forearm was the least itchy spot, and scratching there produced pleasure that was briefer and lower in intensity. Prof Francis McGlone, who led the study, said: "It was interesting that the ankle was the itchiest site and that the most pleasure came from scratching it, because the back has been well-known as a preferred site for scratching."

However, there is no clear explanation for the finding, but one theory is that ankles have evolved as particularly itch-prone because they are likely to come into contact with insects and germs, which could be removed through scratching.

McGlone added: "Generally, if something is nice to do, like scratching an itch, there is a reason for it other than pleasure. It may, for example, that we evolved to feel itch on the ankle and get the most pleasure from scratching it, because our feet were exposed to microbes, fleas and so on."

McGlone believes ankles may have evolved to be more sensitive because they come into contact with insects and germs which could be removed through scratching. "If something is nice to do, like scratching an itch, there is generally a reason for it other than pleasure," he said.

(Agencies)