Medical myths debunked

'Shaving won't make your legs more hairy'
Leg hairs only appear thicker after being shaved because they grow back blunt-ended

Teenage girls have long been warned by their mothers that shaving their legs will make the hair grow back thicker and faster.

However, this conventional wisdom is just a myth, according to researchers in the US who say the thickening is just an optical illusion.

'Shaving won't make your legs more hairy'
Leg hairs only appear thicker after being shaved because they grow back blunt-ended

Scientists at the Indiana University School of Medicine trawled through numerous scientific studies to debunk this, and six other commonly held beliefs which have no basis in truth.

They discovered hair did not grow back faster and darker if shaven, contrary to what most people believe.

The illusion of thicker locks is created because the hair grows back blunt-ended without the fine tapered ends of unshaven hair.

Unlike shaving, waxing causes the hair to grow back finer than before because it pulls the whole hair out by the root.

The team, whose results are published today in the British Medical Journal, also cast doubt on the received wisdom humans should drink eight glasses of water a day, although the recommendation dates back to 1945.

Studies revealed that people get plenty of fluid simply through their consumption of juice, milk and even tea and coffee.

Clinical evidence also highlighted the danger of drinking too much water.

The researchers concluded that an optical illusion may also be responsible for the enduring, but false belief that hair and fingernails continue to grow after a person dies - because the skin retracts after death.

“Dehydration of the body after death and drying or desiccation may lead to the retraction of the skin around the hair or nails,” the report said.

Forensic anthropologist William Maples added: “It is a powerful disturbing image, but it is pure moonshine. No such thing occurs.”

A long-held belief that reading in poor light affects eyesight was also found to be false.

Opthalmologists discovered although bad light could cause temporary eye strain, it was unlikely to have long lasting effects.

Another common belief - in circulation since 1907 - that humans only use 10 per cent of their brains was refuted by studies of patients with brain damage.

They showed damage to any area of the brain had lasting effects on mental, vegetative, and behavioural capabilities, while imaging has revealed no area of the brain was completely inactive.

The researchers also claim to have uncovered the truth about mobile phones in hospitals, revealing that they are not as dangerous as thought.

It was feared the phones interfered with the electromagnetic fields of hospital equipment, but “rigorous testing” in Europe concluded their impact was minimal.

Finally, the idea that eating turkey makes you particularly sleepy was called into question. Turkey contains tryptophan, which is known to cause drowsiness, but far higher levels are found in pork and cheese.